[QNX]Clear transparent regions

If a region gets painted the buffer beneath needs
to be cleared, as it could be that there are
leftovers from the last blit.

Change-Id: I51f19aa010015059e9a6d9d5e5e4f25fb9532d4e
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
QNX: Don't build QNX-only parts on BlackBerry

Only really required source files will be included when building for
BlackBerry.

Change-Id: Ic66b09221c48672358bba7601bc18663ad7fa07a
Reviewed-by: Wolfgang Bremer <wbremer@blackberry.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>