GtkMenuShell: (model binding) show() new items

We weren't calling show() on newly-added items -- make sure we do that.

This makes the Time menu in bloatpad work properly again.

gtk/gtkmenushell.c

@@ -2112,6 +2112,7 @@ gtk_menu_shell_tracker_insert_func (GtkMenuTrackerItem *item,
       g_object_bind_property (item, "accel", widget, "accel", G_BINDING_SYNC_CREATE);
 
       g_signal_connect (widget, "activate", G_CALLBACK (gtk_menu_shell_item_activate), item);
+      gtk_widget_show (widget);
     }
 
   /* TODO: drop this when we have bindings that ref the source */