* clutter/Makefile.am:
* clutter/clutter-stage.c:
* clutter/sdl/Makefile.am:
* clutter/sdl/clutter-backend-sdl.c:
* clutter/sdl/clutter-backend-sdl.h:
* clutter/sdl/clutter-event-sdl.c:
* clutter/sdl/clutter-sdl.h:
* clutter/sdl/clutter-stage-sdl.c:
* clutter/sdl/clutter-stage-sdl.h:
* configure.ac:
Add a basic SDL based backend. Lacks real input event handling
(translation) as yet.
Also allows for clutter to be built against dgles.
