Recreate child windows when changing screens

When setting a new screen, the code calls QWindow::destroy(), which
recursively destroys all child windows. It then calls create() on the
top-level window, leaving child windows destroyed. This causes crashes
if you have embedded native widgets.

Task-number: QTBUG-40817
Change-Id: Iaace2589f48bbfd5faaf5ff95357ff43b310504a
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Bump version

Change-Id: I3aa94110b11e181dea1b8551982ce16dab57f893
QNX: Fix widgets scrolling

Qt expects scroll operations to be executed immediately. They cannot be
postponed since Qt may paint on the scrolled area afterwards.
The new code will only use an accelerated scroll operation (screen_blit)
once before the window is posted, because the blit is from the previous
buffer to the current one. Hence an additional scroll operation could
copy outdated pixel data. Additional scroll operations will be handled
by Qt. Performance issues were not perceived with this approach so far.

Task-number: QTBUG-39958
Change-Id: I6d7c3274c5db6a831a169615518fcdb4d926db70
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>