Text-mode emulation of calling the bindings in keymap.
Creates a text-mode menu of possible choices. You can access the elements
in the menu in two ways:
*) via history mechanism from minibuffer;
*) Or via completion-buffer that is automatically shown.
The last alternative is currently a hack, you cannot use mouse reliably.
MENU is like the MENU argument to `x-popup-menu': either a
keymap or an alist of alists.
DEFAULT-ITEM, if non-nil, specifies an initial default choice.
Its value should be an event that has a binding in MENU.
(fn MENU &optional IN-POPUP DEFAULT-ITEM)