Correction of non reachable links and redirected links in documentation.

The W3C link checker reported a number of problems regarding non reachable links and permanent redirects.
Most of these problems have been fixed with this patch

doc/commands.doc

@@ -433,7 +433,7 @@ Structural indicators
   \par Example:
   \include enum.h
   \htmlonly
-  Click <a href="examples/enum/html/class_test.html">here</a>
+  Click <a href="examples/enum/html/class_enum___test.html">here</a>
   for the corresponding HTML documentation that is generated by doxygen.
   \endhtmlonly
   \latexonly
@@ -565,7 +565,7 @@ Structural indicators
   \par Example:
   \include func.h
   \htmlonly
-  Click <a href="examples/func/html/class_test.html">here</a>
+  Click <a href="examples/func/html/class_fn___test.html">here</a>
   for the corresponding HTML documentation that is generated by doxygen.
   \endhtmlonly
   \latexonly
@@ -823,7 +823,7 @@ Structural indicators
   \par Example:
   \include overload.cpp
   \htmlonly
-  Click <a href="examples/overload/html/class_test.html">here</a>
+  Click <a href="examples/overload/html/class_overload___test.html">here</a>
   for the corresponding HTML documentation that is generated by doxygen.
   \endhtmlonly
   \latexonly
@@ -1121,7 +1121,7 @@ Structural indicators
 
 <hr>
 \section cmdweakgroup \\weakgroup <name> [(title)]
-  \addindex \\addtogroup
+  \addindex \\weakgroup
   Can be used exactly like \ref cmdaddtogroup "\\addtogroup", but has
   a lower priority when it comes to resolving conflicting grouping
   definitions.
@@ -1513,7 +1513,7 @@ ALIASES  = "english=\if english" \
   \par Example:
   \include par.cpp
   \htmlonly
-  Click <a href="examples/par/html/class_test.html">here</a>
+  Click <a href="examples/par/html/class_par___test.html">here</a>
   for the corresponding HTML documentation that is generated by doxygen.
   \endhtmlonly
   \latexonly
@@ -2704,7 +2704,7 @@ class Receiver
 
   \addindex \\startuml
   Starts a text fragment which should contain a valid description of a
-  PlantUML diagram. See http://plantuml.sourceforge.net/ for examples.
+  PlantUML diagram. See http://plantuml.com/ for examples.
   The text fragment ends with \ref cmdenduml "\\enduml".
   \note You need to install Java and the PlantUML's jar file,
   if you want to use this command. The location of the jar file should be specified

doc/customize.doc

@@ -90,7 +90,7 @@ that are disabled by default:
 
 To tweak things like fonts or colors, margins, or other look \& feel
 aspects of the HTML output in detail, you can create a different 
-<a href="http://www.w3schools.com/css/default.asp">cascading style sheet</a>. 
+<a href="https://www.w3schools.com/css/default.asp">cascading style sheet</a>. 
 You can also let doxygen use a custom header and footer for each HTML 
 page it generates, for instance to make the output conform to the style 
 used on the rest of your web site.
@@ -390,7 +390,7 @@ files as one big DOM tree would not fit into memory.
 
 See <a href="https://github.com/michaeljones/breathe">the Breathe project</a> for
 an example that uses doxygen XML output from Python to bridge it with the 
-<a href="http://sphinx.pocoo.org/">Sphinx</a> document generator.
+<a href="http://www.sphinx-doc.org/en/stable/">Sphinx</a> document generator.
 
 
 \htmlonly

doc/docblocks.doc

@@ -260,7 +260,7 @@ Here is an example of the use of these comment blocks:
 \include afterdoc.h
  \htmlonly
  </p>
- Click <a href="examples/afterdoc/html/class_test.html">here</a>
+ Click <a href="examples/afterdoc/html/class_afterdoc___test.html">here</a>
  for the corresponding HTML documentation that is generated by doxygen.
  \endhtmlonly
  \latexonly
@@ -281,7 +281,7 @@ Here is an example of a documented piece of C++ code using the Qt style:
 \include qtstyle.cpp
  \htmlonly
  </p>
- Click <a href="examples/qtstyle/html/class_test.html">here</a>
+ Click <a href="examples/qtstyle/html/class_q_tstyle___test.html">here</a>
  for the corresponding HTML documentation that is generated by doxygen.
  \endhtmlonly
  \latexonly
@@ -316,7 +316,7 @@ JavaDoc style and \ref cfg_javadoc_autobrief "JAVADOC_AUTOBRIEF" set to YES:
 \include jdstyle.cpp
  \htmlonly
  </p>
- Click <a href="examples/jdstyle/html/class_test.html">here</a>
+ Click <a href="examples/jdstyle/html/class_javadoc___test.html">here</a>
  for the corresponding HTML documentation that is generated by doxygen.
  \endhtmlonly
  \latexonly
@@ -634,7 +634,7 @@ need for some more structure, like a block of verbatim text, a list, or a
 simple table. For this doxygen supports the 
 <a href="http://daringfireball.net/projects/markdown/syntax">Markdown</a> 
 syntax, including parts of the
-<a href="http://michelf.com/projects/php-markdown/extra/">Markdown Extra</a>
+<a href="https://michelf.ca/projects/php-markdown/extra/">Markdown Extra</a>
 extension. 
 
 Markdown is designed to be very easy to read and write. 
@@ -646,13 +646,13 @@ directly. For more details see chapter \ref markdown.
 For programming language specific formatting doxygen has two
 forms of additional markup on top of Markdown formatting.
 
-1. <a href="http://en.wikipedia.org/wiki/Javadoc">Javadoc</a> like markup.
+1. <a href="https://en.wikipedia.org/wiki/Javadoc">Javadoc</a> like markup.
    See \ref commands for a complete overview of all commands supported by doxygen.
-2. <a href="http://en.wikipedia.org/wiki/C_Sharp_(programming_language)#XML_documentation_system">XML</a> markup
+2. <a href="https://en.wikipedia.org/wiki/C_Sharp_(programming_language)#XML_documentation_system">XML</a> markup
    as specified in the C# standard. See \ref xmlcmds for the XML commands supported by doxygen.
 
 If this is still not enough doxygen also supports a \ref htmlcmds "subset" of 
-the <a href="http://en.wikipedia.org/wiki/HTML">HTML</a> markup language.
+the <a href="https://en.wikipedia.org/wiki/HTML">HTML</a> markup language.
 
 \htmlonly
 Go to the <a href="markdown.html">next</a> section or return to the

doc/extsearch.doc

@@ -52,7 +52,7 @@ The data flow is shown in the following diagram:
 
 The first step is to make the search engine available via a web server.
 If you use `doxysearch.cgi` this means making the
-<a href="http://en.wikipedia.org/wiki/Common_Gateway_Interface">CGI</a> binary
+<a href="https://en.wikipedia.org/wiki/Common_Gateway_Interface">CGI</a> binary
 available from the web server (i.e. be able to run it from a 
 browser via an URL starting with http:)
 
@@ -187,7 +187,7 @@ The next subsections describe these interfaces in more detail.
 \subsection extsearch_api_index Indexer input format
 
 The search data produced by doxygen follows the 
-<a href="http://wiki.apache.org/solr/UpdateXmlMessages">Solr XML index message</a>
+<a href="https://wiki.apache.org/solr/UpdateXmlMessages">Solr XML index message</a>
 format.
 
 The input for the indexer is an XML file, which consists of one `<add>` tag containing 
@@ -224,12 +224,12 @@ Each field has a name. The following field names are supported:
 - *text*: the documentation associated with the item. Note that only words are present, no markup.
 
 @note Due to the potentially large size of the XML file, it is recommended to use a 
-<a href="http://en.wikipedia.org/wiki/Simple_API_for_XML">SAX based parser</a> to process it.
+<a href="https://en.wikipedia.org/wiki/Simple_API_for_XML">SAX based parser</a> to process it.
 
 \subsection extsearch_api_search_in Search URL format
 
 When the search engine is invoked from a doxygen generated HTML page, a number of parameters are
-passed to via the <a href="http://en.wikipedia.org/wiki/Query_string">query string</a>.
+passed to via the <a href="https://en.wikipedia.org/wiki/Query_string">query string</a>.
 
 The following fields are passed:
 - *q*:  the query text as entered by the user
@@ -247,14 +247,14 @@ It represents a query for the word 'list' (`q=list`) requesting 20 search result
 starting with the result number 20 (`p=1`) and using callback 'dummy' (`cb=dummy`):
 
 
-@note The values are <a href="http://en.wikipedia.org/wiki/Percent-encoding">URL encoded</a> so they
+@note The values are <a href="https://en.wikipedia.org/wiki/Percent-encoding">URL encoded</a> so they
 have to be decoded before they can be used.
 
 \subsection extsearch_api_search_out Search results format
 
 When invoking the search engine as shown in the previous subsection, it should reply with
 the results. The format of the reply is
-<a href="http://en.wikipedia.org/wiki/JSONP">JSON with padding</a>, which is basically
+<a href="https://en.wikipedia.org/wiki/JSONP">JSON with padding</a>, which is basically
 a javascript struct wrapped in a function call. The name of function should be the name of
 the callback (as passed with the *cb* field in the query).
 

doc/faq.doc

@@ -285,7 +285,7 @@ At the time I was looking into \c lex and \c yacc, where a lot of things start w
 \section faq_why What was the reason to develop doxygen?
 
 I once wrote a GUI widget based on the Qt library (it is still available at
-http://sourceforge.net/projects/qdbttabular/ but hasn't been updated since 2002). 
+https://sourceforge.net/projects/qdbttabular/ but hasn't been updated since 2002). 
 Qt had nicely generated documentation (using an internal tool which 
 <a href="http://rant.gulbrandsen.priv.no/udoc/history">they didn't want to release</a>) 
 and I wrote similar docs by hand. 

doc/formulas.doc

@@ -30,7 +30,7 @@ have the following tools installed
     to bitmaps. I have used Aladdin GhostScript 8.0 for testing.
 </ul>
 For the HTML output there is also an alternative solution using
-<a href="http://www.mathjax.org">MathJax</a> which does not
+<a href="https://www.mathjax.org">MathJax</a> which does not
 require the above tools. If you enable \ref cfg_use_mathjax "USE_MATHJAX" in
 the config then the latex formulas will be copied to the HTML "as is" and a
 client side javascript will parse them and turn them into (interactive) images.

doc/grouping.doc

@@ -197,7 +197,7 @@ documentation of the class.
 
 \htmlonly
 </p>
-Click <a href="examples/memgrp/html/class_test.html">here</a> 
+Click <a href="examples/memgrp/html/class_memgrp___test.html">here</a> 
 for the corresponding HTML documentation that is generated by doxygen.
 \endhtmlonly
 \latexonly

doc/index.doc

@@ -180,7 +180,7 @@ Thanks go to:
 <li>Talin for adding support for C# style comments with XML markup.
 <li>Petr Prikryl for coordinating the internationalization support.
     All language maintainers for providing translations into many languages.
-<li>The band <a href="http://www.porcupinetree.com">Porcupine Tree</a> for 
+<li>The band <a href="http://www.porcupinetree.com/">Porcupine Tree</a> for 
     providing hours of great music to listen to while coding.
 <li>many, many others for suggestions, patches and bug reports.
 </ul>

doc/install.doc

@@ -37,7 +37,7 @@ following to build the executable:
     \addindex strip
     \addindex python
 <li>In order to generate a \c Makefile for your platform, you need 
-    <a href="http://www.cmake.org/">cmake</a> version 2.8.12 or later.
+    <a href="https://cmake.org/">cmake</a> version 2.8.12 or later.
     \addindex cmake
 </ul>
 
@@ -63,7 +63,7 @@ tools should be installed.
 <li>For formulas in the HTML output (when MathJax is not used)
     or in case you do not wish to use `pdflatex,
     the ghostscript interpreter is needed. You can find it at 
-    <a href="http://www.ghostscript.com/">www.ghostscript.com</a>.
+    <a href="https://www.ghostscript.com/">www.ghostscript.com</a>.
 </ul>
 
 Compilation is now done by performing the following steps:
@@ -150,20 +150,20 @@ standard installation procedure that is required for these packages.
 \section install_src_windows Compiling from source on Windows
 
 From version 1.8.10 onwards, build files need to be generated by cmake.
-cmake can be downloaded from http://www.cmake.org/download/
+cmake can be downloaded from https://cmake.org/download/
 
 At the moment only the express version of Visual Studio 2013 is tested,
 but other version might also work.
 
 Alternatively, you can compile doxygen 
 \ref install_src_unix "the UNIX way" using 
-<a href="http://en.wikipedia.org/wiki/Cygwin">Cygwin</a>
+<a href="https://en.wikipedia.org/wiki/Cygwin">Cygwin</a>
 or <a href="http://www.mingw.org/">MinGW</a>.
 
 The next step is to install modern versions of \c bison and \c flex
-(see http://sourceforge.net/projects/winflexbison. After installation and adding them to
+(see https://sourceforge.net/projects/winflexbison/. After installation and adding them to
 your `path` rename `win_flex.exe` to `flex.exe` and `win_bison.exe` to `bison.exe`)
-Furthermore you have to install \c python (version 2.6 or higher, see http://www.python.org).
+Furthermore you have to install \c python (version 2.6 or higher, see https://www.python.org).
 These packages are needed during the compilation process.
 
 Download doxygen's source tarball and put it somewhere (e.g. use <code>c:\\tools</code>)
@@ -214,19 +214,19 @@ you need qhelpgenerator which is part of Qt.
 You can download Qt from <a href="http://qt-project.org/downloads">Qt Software Downloads</a>.
 
 In order to generate PDF output or use scientific formulas you will also need to
-install <a href="http://en.wikipedia.org/wiki/LaTeX">LaTeX</a> and 
-<a href="http://en.wikipedia.org/wiki/Ghostscript">Ghostscript</a>. 
+install <a href="https://en.wikipedia.org/wiki/LaTeX">LaTeX</a> and 
+<a href="https://en.wikipedia.org/wiki/Ghostscript">Ghostscript</a>. 
 
 For \LaTeX a number of distributions exists. Popular ones that should work with
-doxygen are <a href="http://www.miktex.org">MikTex</a> 
+doxygen are <a href="https://miktex.org/">MikTex</a> 
 and <a href="http://www.tug.org/protext/">proTeXt</a>.
 
-Ghostscript can be <a href="http://sourceforge.net/projects/ghostscript/">downloaded</a> 
+Ghostscript can be <a href="https://sourceforge.net/projects/ghostscript/">downloaded</a> 
 from Sourceforge.
 
 After installing \LaTeX and Ghostscript you'll need to make sure the tools
 latex.exe, pdflatex.exe, and gswin32c.exe are present in the search path of a
-command box. Follow <a href="http://www.computerhope.com/issues/ch000549.htm">these</a>
+command box. Follow <a href="https://www.computerhope.com/issues/ch000549.htm">these</a>
 instructions if you are unsure and run the commands from a command box to verify it works.
 
 \htmlonly

doc/markdown.doc

@@ -41,9 +41,9 @@ the extensions that doxygen supports.
 Finally section \ref markdown_dox discusses some specifics for doxygen's
 implementation of the Markdown standard.
 
-[markdown]: http://daringfireball.net/projects/markdown 
-[mdextra]:  http://michelf.com/projects/php-markdown/extra/
-[github]:   http://github.github.com/github-flavored-markdown/
+[markdown]: http://daringfireball.net/projects/markdown/ 
+[mdextra]:  https://michelf.ca/projects/php-markdown/extra/
+[github]:   https://github.github.com/github-flavored-markdown/
 
 \section markdown_std Standard Markdown
 
@@ -303,7 +303,7 @@ Note that using `[TOC]` is the same as using a
 \subsection md_tables Tables
 
 Of the features defined by "Markdown Extra" is support for
-<a href="http://michelf.com/projects/php-markdown/extra/#table">simple tables</a>:
+<a href="https://michelf.ca/projects/php-markdown/extra/#table">simple tables</a>:
 
 A table consists of a header line, a separator line, and at least one
 row line. Table columns are separated by the pipe (|) character.
@@ -376,7 +376,7 @@ For more complex tables in doxygen please have a look at: \ref tables
 \subsection md_fenced Fenced Code Blocks
 
 Another feature defined by "Markdown Extra" is support for
-<a href="http://michelf.com/projects/php-markdown/extra/#fenced-code-blocks">
+<a href="https://michelf.ca/projects/php-markdown/extra/#fenced-code-blocks">
 fenced code blocks</a>:
 
 A fenced code block does not require indentation, and is

doc/searching.doc

@@ -72,7 +72,7 @@ has its own advantages and disadvantages:
    searching, meaning that you could use your own indexer and search engine 
    of choice. To make life easier doxygen ships with an example indexer 
    (doxyindexer) and search engine (doxysearch.cgi) based on 
-   the <a href="http://xapian.org/">Xapian</a> open source search engine 
+   the <a href="https://xapian.org/">Xapian</a> open source search engine 
    library.
 
    To enable this search method set 
@@ -147,7 +147,7 @@ has its own advantages and disadvantages:
    \ref cfg_qhp_namespace "QHP_NAMESPACE", 
    \ref cfg_qhg_location "QHG_LOCATION", 
    \ref cfg_qhp_virtual_folder "QHP_VIRTUAL_FOLDER".
-   See <a href="http://doc.qt.digia.com/qq/qq28-qthelp.html#htmlfilesandhelpprojects">this article</a> 
+   See <a href="http://doc.qt.io/archives/qq/qq28-qthelp.html#htmlfilesandhelpprojects">this article</a> 
    for more info.
 
    Feature wise the Qt compressed help feature is comparable with the CHM 

doc/starting.doc

@@ -263,7 +263,7 @@ capabilities of the man page format, so some information
 \subsection docbook_out DocBook output
 \addindex docbook
 Doxygen can also generate output in the 
-<a href="http://www.docbook.org/">DocBook</a> format. How to process the
+<a href="http://docbook.org/">DocBook</a> format. How to process the
 DocBook output is beyond the scope of this manual.
 
 \section step3 Step 3: Documenting the sources