refactored LoadingScene and revised util::bmfont to use OpenGL. partial GLES conversion in progress.
prepare_surface_for_texture now handles a possibility of BGR/ABGR pixel format.
guarantees that STAGEFILEs ignore alpha channels in any case.
GraphicDisplay::render got converted, with an exception of BGAs.
introduced PreparedSurface; BGA is now rendered via OpenGL.