This exposes a clutter_wayland_surface_set_surface() function. The
implementation ignores requests to re-set the same surface and since now
has code to cleanup old surface state before setting the new surface.
(previously the surface was construct only so this wasn't necessary)
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>