Fix use uninitialized, detected by GCC 4.8

If the widget \a field is not present on this form, getWidgetPosition
might not fill in the role variable. GCC is correct.

qformlayout.cpp:1690:19: error: ‘role’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

Change-Id: Ia67991a71e8f1ceacb9d6370c7028c454ef630c6
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Atomics: implement fetchAndSub on top of fetchAndAdd

Instead of looping unnecessarily on top of testAndSet.

Task-number: QTBUG-37031
Change-Id: I8120f8405eb76dccc9066749cee0a92b0f2da20e
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Sergio Ahumada <sahumada@blackberry.com>
Remove deleted QNetworkReplies from SPDY queues

We already remove QNetworkReply from most queues, but we also need
to remove it from the SPDY queue. Otherwise we might end up trying
to send an already deleted message.

Change-Id: Ib39bf8f26315b66179755a6f66dbd657576cbbe3
Reviewed-by: Peter Hartmann <phartmann@blackberry.com>
Remove the header precompilation for QtXml and QtOpenGLExtensions

Respectively, those modules have 2 and 1 source files. Precompilation costs
more than the benefit of using precompiled headers.

Change-Id: I15ababd9ba7cce2e1510454da49010456ff0597a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>