Doc: Enabled crosslinking for Qt X11 Extras and Qt Serial Port

Added link to Qt X11 Extras in Supported Platforms

Change-Id: I2d128e3d4c9acff3e40258afd218d40c4847bbb6
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>

doc/config/qtdoc-project.qdocconf

@@ -33,6 +33,7 @@ depends += \
     qtscript \
     qtscripttools \
     qtsensors \
+    qtserialport \
     qtserviceframework \
     qtsql \
     qtsvg \
@@ -44,6 +45,7 @@ depends += \
     qtwidgets \
     qtwebkit \
     qtwebkitexamples \
+    qtx11extras \
     qtxml \
     qtxmlpatterns
 

doc/src/platforms/supported-platforms.qdoc

@@ -75,6 +75,7 @@
         \li \l{Network programming with Qt}{Networking}, \l{QtXml Module}
         {XML} and \l{SQL in Qt}{database} functionality
         \li \l{ECMAScript Reference}{ECMA standard} scripting engine
+        \li \l{Qt X11 Extras} - provides APIs for X11
     \endlist
 
     \section2 Integrated Development Tools