Partially revert "Move notification of layout change up from QApplication to QGuiApplication."

We can't rely on QGuiApplication::topLevelWindows containing top level QWidgets,
because they only exist as actual windows once QWidgetPrivate::create_sys is
called. Thus, make sure to send notifications to all top level widgets, if a
QApplication is being used.

This reverts commit f82ed5b3e30282bb8dc1da321a0d04ad4d463e59.

Task-number: QTBUG-35589
Change-Id: Iac517089af1c22f20094ba6e185d5ed44ebe3d6f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Correct debug bit setting with WGL

No need to tie the debug bit to OpenGL 3.0+. xcb is correct
in this respect, let's correct the windows plugin too.

Change-Id: I13ea48de067d3fb61575be8f71b97bb547d8eb02
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>