Bug 1158154 - Add gtk_window_set_auto_startup_notification to mozgtk stubs. r=nical

widget/gtk/mozgtk/mozgtk.c

@@ -437,6 +437,7 @@ STUB(gtk_widget_realize)
 STUB(gtk_widget_reparent)
 STUB(gtk_widget_set_allocation)
 STUB(gtk_widget_set_app_paintable)
+STUB(gtk_window_set_auto_startup_notification)
 STUB(gtk_widget_set_can_focus)
 STUB(gtk_widget_set_direction)
 STUB(gtk_widget_set_double_buffered)