Fix link to create a pull request and to git download (#4817)

* fixing link to create a pull request

* fixing link in git exe

Git for Windows 1.x is deprecated, superseded by Git for Windows 2.x.

Author: All4Gis

INSTALL

@@ -747,7 +747,7 @@ successful install, they're not needed anymore.
 In order to check out QGIS sources from the repository, you need a git client.
 This installer should work fine:
 
-http://msysgit.googlecode.com/files/Git-1.7.4-preview20110204.exe
+https://github.com/git-for-windows/git/releases/download/v2.13.2.windows.1/Git-2.13.2-32-bit.exe (32bit) or https://github.com/git-for-windows/git/releases/download/v2.13.2.windows.1/Git-2.13.2-64-bit.exe (64bit)
 
 
     4.2.6. CMake

README.md

@@ -72,7 +72,7 @@ You can get support in the following ways:
 
 QGIS is on GitHub at https://github.com/qgis/QGIS. If you wish to contribute
 patches you can [fork the project](https://help.github.com/forking/), make your changes, commit to your
-repository, and then [issue a pull request](http://help.github.com/pull-requests/). The development team can then
+repository, and then [create a pull request](https://help.github.com/articles/creating-a-pull-request-from-a-fork/). The development team can then
 review your contribution and commit it upstream as appropriate.
 If you commit a new feature, add [FEATURE] to your commit message AND give a clear description of the new feature. A webhook will automatically create an issue on the QGIS-Documentation repo to tell people to write documentation about it.
 

doc/INSTALL.html

@@ -1088,7 +1088,7 @@ <H3>4.2.5. git</H3>
 This installer should work fine:
 </P>
 <P>
-<A HREF="http://msysgit.googlecode.com/files/Git-1.7.4-preview20110204.exe">http://msysgit.googlecode.com/files/Git-1.7.4-preview20110204.exe</A>
+<A HREF="https://git-scm.com/download/win">https://git-scm.com/download/win</A>
 </P>
 
 <H3>4.2.6. CMake</H3>

doc/msys.t2t

@@ -115,7 +115,7 @@ successful install, they're not needed anymore.
 In order to check out QGIS sources from the repository, you need a git client.
 This installer should work fine:
 
-http://msysgit.googlecode.com/files/Git-1.7.4-preview20110204.exe
+https://git-scm.com/download/win
 
 === CMake ===