Fix gdk_cairo_region_create_from_surface on big endian

Fix gdk_cairo_region_create_from_surface on big endian

gdk_cairo_region_create_from_surface doesn't work correctly on PPC.
This is most prominently seen with the GTK window resize grip, the
shape of which is mirrored every eight pixels horizontally.

At the same time, use an A1 surface for the resize grip shape to
eliminates an A8->A1 surface conversion.