When the source rectangle needs to flip and it doesn't fit in the
source device area, the destination image is flipped but the
destination area isn't flipped.  GdiAlphaBlend doesn't support
mirroring, the above isn't applicable.
Signed-off-by: Akihiro Sagawa <sagawa.aki@gmail.com>
Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>