Rework/reorder of the code. Each case has been separated into another

Rework/reorder of the code. Each case has been separated into another

1999-11-20  Michael Zucchi  <zucchi@zedzone.mmc.com.au>

        * src/gdk-pixbuf-drawable.c (gdk_pixbuf_from_drawable_core):
        Rework/reorder of the code.  Each case has been separated into
        another function; its big but it should be quick.
        gdk_pixbuf_rgba_from_drawable() will now return a pixbuf with
        opaque alpha information.  Not all depths/formats have been
        tested, but 8, 15/16 and 24 (alinged 32) should work ok.