Fusion Style: Workaround to get combo box item style from QtQuick Ctrls

This is to align the behaviour with how QGtkStyles behavior is.

Change-Id: Ic85d96cf4a4ab30974b25936de6d5b98e65dd2f3
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Add Grayscale8 and Alpha8 formats to QImage and drawing

Extend the QImage format with two 8-bit grayscale and alpha formats.
These formats have the advantage over Indexed8 that they have simpler
conversion and can be rendered to by the raster engine.

[ChangeLog][QtGui][QImage] Added support grayscale and alpha 8-bit
formats which can also be rendered to.

Change-Id: I4343c80a92a3dda196aa38d0c3ea251b094fc274
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>