wayland/x11: Set constraints on the CoglRenderer

When using the Wayland backend this sets a constraint that the
CoglRenderer selects the Wayland EGL winsys.

When a Wayland compositor display is set it now also sets a constraint
that the render should use EGL because only EGL renderers will set up
the required wl_drm global object.

The X11 backend now sets the X11 constraint.

Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>

clutter/wayland/clutter-backend-wayland.c

@@ -215,6 +215,8 @@ clutter_backend_wayland_get_renderer (ClutterBackend  *backend,
 
   renderer = cogl_renderer_new ();
 
+  cogl_renderer_set_winsys_id (renderer, COGL_WINSYS_ID_EGL_WAYLAND);
+
   cogl_wayland_renderer_set_foreign_display (renderer,
                                              backend_wayland->wayland_display);
   cogl_wayland_renderer_set_foreign_compositor (renderer,