shaped-texture: Add support for texture transform

This adds the necessary bits to support Wayland buffer transforms.
The main part here is to properly setup the Cogl pipeline
and to recalculate the size of the painted area accordingly,
so culling etc. still works.

The choosen approach additionally lays groundwork for Wayland
wp_viewporter support.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/322

src/compositor/meta-surface-actor.h

@@ -5,6 +5,7 @@
 
 #include "config.h"
 
+#include "backends/meta-backend-types.h"
 #include "meta/meta-shaped-texture.h"
 #include "meta/window.h"
 
@@ -76,6 +77,8 @@ void meta_surface_actor_set_unredirected (MetaSurfaceActor *actor,
                                           gboolean          unredirected);
 gboolean meta_surface_actor_is_unredirected (MetaSurfaceActor *actor);
 
+void meta_surface_actor_set_transform (MetaSurfaceActor     *self,
+                                       MetaMonitorTransform  transform);
 G_END_DECLS
 
 #endif /* META_SURFACE_ACTOR_PRIVATE_H */