Ordinary GTK button in menubar

[Enno Fennema <e fennema tiscali nl>]

Apart from gtk_menu_items that pop up submenus I would like an ordinary
button in the menubar, which when clicked performs an action.

I can connect a handler to a gtk_menu_item but then I need two clicks on
it to call the handler once (some select/deselect or activate/deactivate
?? ).

Can anyone tell me how to get ordinary button behaviour (one click, one
handler call) for an item in a menu-bar?

Your assistance is appreciated,
Enno Fennema