QString: avoid a QLocale detach in vsprintf

I didn't dig deeper to check where the additional reference came from,
but tracing confirmed that the QSharedDataPointer<QLocalePrivate>::detach()
call is gone with this change.

Background:
QString::vsprintf is used in the logging framework, and as such shouldn't
waste any memory. It's currently anyway unusable from, say, signal handlers,
but this is low-hanging fruit that shaves off one of the dozen or so
memory allocations involved in a simple qFatal() call.

Change-Id: I19fa2148f669dfc7b5f276221151e25a4348cbfe
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Add missing implementation in QAccessibleTabBar::indexOfChild

This avoids the assertion in iaccessible2.cpp(510)

Change-Id: I1a4c007ffcbcda70f0e37ef3cf55a303683b58c1
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Don't try to allocate a msaa FBO when it is not supported.

Change-Id: Ib4bdabcfa4e9b76156d7188da82fe2173b4b997e
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
QMessageBox - make it possible to have a checkbox on the dialog

This (partly) solves

Task-number: QTBUG-2450

Change-Id: Ie2280c87b96e72acc76e806a83c4e8cc0d4e4ee4
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>