Doc: Adding platform extras example pages into the main examples page.

-better visibility to those examples.
-also added Active Qt link.

Change-Id: I3f4aa3e967bd3618f8739dfcdd5b4ba1ea5ee4e5
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>

doc/src/examples.qdoc

 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the documentation of the Qt Toolkit.
@@ -75,6 +75,13 @@
         \endlist
     \enddiv
     \div {class="icons1of3"}
+        \b{Platform-Specific Extras}
+        \list
+        \li \l{Qt Android Extras Examples}{Android Extras}
+        \li \l{Qt Mac Extras Examples}{Mac Extras}
+        \li \l{Qt Windows Extras Examples}{Windows Extras}
+        \li \l{Active Qt#Examples}{Active Qt Examples}
+        \endlist
     \enddiv
     \enddiv