decompose wl_stubs.c: move icon painting functions to wl_icon.c

src/backend/wayland/wl_stubs.c

@@ -170,6 +170,9 @@ void wl_noop_icon_update_pixmap(WIcon *icon) { (void)icon; }
  * Called at the end of wIconPaint() in icon.c so the backend finalises the
  * surface after the policy layer has set up icon->file_image etc.
  */
+
+
+
 void wl_noop_restore_desktop(WScreen *scr) { (void)scr; }
 void wl_noop_wipe_desktop(WScreen *scr) { (void)scr; }