cairo-util: return theme location from frame_touch_down

I'll be using this in a follow up patch that adds touch input to weston's
wayland backend.

Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
diff --git a/shared/cairo-util.h b/shared/cairo-util.h
index 019424e..4fee087 100644
--- a/shared/cairo-util.h
+++ b/shared/cairo-util.h
@@ -210,7 +210,7 @@
 frame_pointer_button(struct frame *frame, void *pointer,
 		     uint32_t button, enum frame_button_state state);
 
-void
+enum theme_location
 frame_touch_down(struct frame *frame, void *data, int32_t id, int x, int y);
 
 void