wayland-winsys: Provide a wl_registry.global_remove callback

Otherwise libwayland-client will abort() when we get that event.

https://bugzilla.gnome.org/show_bug.cgi?id=743594

cogl/winsys/cogl-winsys-egl-wayland.c

@@ -114,6 +114,14 @@ registry_handle_global_cb (void *data,
       wl_registry_bind (registry, id, &wl_shell_interface, 1);
 }
 
+static void
+registry_handle_global_remove_cb (void *data,
+                                  struct wl_registry *registry,
+                                  uint32_t name)
+{
+  /* Nothing to do for now */
+}
+
 static void
 _cogl_winsys_renderer_disconnect (CoglRenderer *renderer)
 {
@@ -137,6 +145,7 @@ _cogl_winsys_renderer_disconnect (CoglRenderer *renderer)
 
 static const struct wl_registry_listener registry_listener = {
   registry_handle_global_cb,
+  registry_handle_global_remove_cb
 };
 
 static int64_t