They are unreliable because every type checking cast discards them,
they are useless anyway, visual clutter, added inconsistently, and
generally suck. Wanted to do this a long time ago, it was a bad idea
in the first place.
- don't include <gdk-pixbuf/gdk-pixbuf.h> in headers in app/
- instead, include it in many .c files instead of <glib-object.h>,
finally acknowledging the fact that app/ depends on gdk-pixbuf almost
globally
- fix up includes as if libgimpbase depended in GIO, which it soon will
