gtk+ 2.3 hidden menubar keybindings / BonoboWindow

Hi,

after a gtk+ change between 2.3.0 and 2.3.1, a menu's keybindings get
disabled when the menu is hidden. This can be overridden, e.g.

http://bugzilla.gnome.org/show_bug.cgi?id=129349

I want to do this in a BonoboWindow (I hide the menubar for fullscreen
mode, but don't want to lose the keybindings). Of course, there's no
public GtkMenubar. What can I do?

Thanks,
	Martin