weston-pointer: Add destroy signal

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
diff --git a/libweston/compositor.h b/libweston/compositor.h
index 4177756..39f39c1 100644
--- a/libweston/compositor.h
+++ b/libweston/compositor.h
@@ -370,6 +370,7 @@
 	struct wl_listener focus_resource_listener;
 	struct wl_signal focus_signal;
 	struct wl_signal motion_signal;
+	struct wl_signal destroy_signal;
 
 	struct weston_view *sprite;
 	struct wl_listener sprite_destroy_listener;