Doc: Updated url variable in qdocconf files.

In 5.2, the HTML output is in a flatter structure and when they are
hosted in qt-project.org/doc, the documentation will be found at
http://qt-project.org/doc/qt-$QT_VER



The url variable is used by projects outside of Qt 5 which need
to link to Qt 5 documentation, such as Qt Creator.

Task-number: QTBUG-34584
Change-Id: I7f989870b311e101ed4de85f3139f010012cfd71
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>

src/xmlpatterns/doc/qtxmlpatterns.qdocconf

@@ -2,6 +2,7 @@ include($QT_INSTALL_DOCS/global/qt-module-defaults.qdocconf)
 
 # Name of the project which must match the outputdir. Determines the .index file
 project = QtXmlPatterns
+url = http://qt-project.org/doc/qt-$QT_VER
 
 # Directories in which to search for files to document and images.
 # By default set to the root directory of the project for sources