A menu item used to tear off and reattach its menu
A <gtk-tearoff-menu-item> is a special <gtk-menu-item> which is
used to tear off and reattach its menu.
When its menu is shown normally, the <gtk-tearoff-menu-item> 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 <gtk-tearoff-menu-item> 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.