[fix] doc/book: Fixing custom HTML for running sources.

As the previous solution only worked for generated HTML and not for
the PDF. Replacing it with simple un-styled links. Will have to
come up with a better solution...

doc/book/hello_chat/hello_chat.adoc

@@ -38,9 +38,7 @@ If you are curious, this is the full source code of the application:
 ------------------------
 include::hello_chat.opa[]
 ------------------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_chat">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_chat[Run]
 
 In this listing, we define the communication infrastructure for the chatroom,
 the user interface, and finally, the main application. In the rest of the
@@ -595,9 +593,7 @@ As a summary, let us recapitulate the source file:
 ------------------------
 include::hello_chat.opa[]
 ------------------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_chat">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_chat[Run]
 
 All this in 20 effective lines of code (without the CSS). Note that, in this
 final version, we have removed some needless parentheses, which were useful

doc/book/hello_recaptcha/hello_recaptcha.adoc

@@ -34,9 +34,7 @@ If you are curious, this is the full source code of our application:
 ------------------------
 include::hello_recaptcha_app.opa[]
 ------------------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_recaptcha">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_recaptcha[Run]
 
 Of course, since the features are provided by Google reCaptcha, the most
 interesting aspects of the code are not to be found in the source of the
@@ -778,9 +776,7 @@ To test the API, we may write a simple application:
 ------------------------
 include::hello_recaptcha_app.opa[]
 ------------------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_recaptcha">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_recaptcha[Run]
 
 With the exception of directive +@server_private+, this listing should not
 surprise you. Here, we placed directive +@server_private+ as a sanity check, to

doc/book/hello_web_services/hello_web_services.adoc

@@ -42,9 +42,7 @@ If you are curious, this is the full source code of the REST wiki server:
 -------------
 include::hello_wiki_rest.opa[]
 -------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_wiki_rest">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_wiki_rest[Run]
 
 We will now walk through the concepts introduced in this listing.
 
@@ -185,9 +183,7 @@ And with this, we are done! Our wiki can now be scripted by external web applica
 ----------------
 include::hello_wiki_rest.opa[]
 ----------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_wiki_rest">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_wiki_rest[Run]
 
 All in all, the changes required a dozen lines of code.
 
@@ -417,9 +413,7 @@ If you are curious, this is the full source code of the REST wiki client (which
 -------------
 include::hello_wiki_rest_client_customizable.opa[]
 -------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_wiki_rest_client">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_wiki_rest_client[Run]
 
 The web client
 ~~~~~~~~~~~~~~
@@ -672,9 +666,7 @@ With this, your client wiki is complete:
 ----------------
 include::hello_wiki_rest.opa[]
 ----------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_wiki_rest">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_wiki_rest[Run]
 
 Launch the server wiki, launch the client wiki on a different port (use option
 +--server-port+ to select a port) and behold, you can edit your wiki from two
@@ -907,9 +899,7 @@ The full source code follows:
 --------------
 include::hello_wiki_rest_client_customizable.opa[]
 --------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_wiki_rest_client">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_wiki_rest_client[Run]
 
 Exercises
 ~~~~~~~~~

doc/book/hello_wiki/hello_wiki.adoc

@@ -35,9 +35,7 @@ If you are curious, this is the full source code of the application.
 ------------------------
 include::hello_wiki.opa[]
 ------------------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_wiki">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_wiki[Run]
 
 In this listing, we define a database for storing the content of the pages in a
 safe format, we define the user interface and finally, the main application.  In
@@ -402,9 +400,7 @@ As a summary, let us recapitulate the source file:
 ------------------------
 include::hello_wiki_simple.opa[]
 ------------------------
-++++
-<span class="run"><A target="_blank" href="http://tutorials.opalang.org/hello_wiki">Run</A></span>
-++++
+http://tutorials.opalang.org/hello_wiki[Run]
 
 This is a total of 30 effective lines of code + CSS.