Merge branch 'surface-synced-single-alloc' into 'master'

compositor: use a single allocation for all synced states

See merge request wlroots/wlroots!4495

include/wlr/types/wlr_compositor.h

@@ -72,6 +72,8 @@ struct wlr_surface_state {
 
 	// Sync'ed object states, one per struct wlr_surface_synced
 	struct wl_array synced; // void *
+	// Buffer for synced states
+	void *synced_buffer;
 };
 
 struct wlr_surface_role {