I also replaced sal_Bool with bool. It's a private class so this is safe;
only salBool GraphicCache::FillSwappedGraphicObject() leaks to bool to
the world.

I also removed the unused Dummy class members.

I also removed some unused methods.

 - the cairo_set_source_rgba should be called with non-alpha-pre-multiplied
   color values
 - fixes fdo#33591 and fdo#35681