A GTK2.TearoffMenuItem is a special W(MenuItem) which is used to
tear off and reattach its menu.
When its menu is shown normally, the GTK2.TearoffMenuItem is drawn
as a dotted line indicating that the menu can be torn
off. Activating it causes its menu to be torn off and displayed in
its own window as a tearoff menu.
When its menu is shown as a tearoff menu, the GTK2.TearoffMenuItem
is drawn as a dotted line which has a left pointing arrow graphic
indicating that the tearoff menu can be reattached. Activating it
will erase the tearoff menu window.
GTK2.TearoffMenuItem()->set_size_request(100,0)
GTK2.Table()->set_row_spacings()