Minor issue: How do we make iconic command menus? Probably another keyword... | SWM

When type is :command, value must be a command (a cons of a command name followed by
a list of the command's arguments), or a command name. (When value is a command name,
it behaves as though a command with no arguments was supplied.) In the case where all
of the command's required arguments are supplied, clicking on an item in the menu invokes
the command immediately. Otherwise, the user will be prompted for the remaining required
arguments.

When type is :function, value must be function having indefinite extent that, when called,
returns a command. The function is called with two arguments, the gesture the user used to
select the item (either a keyboard or button press event) and a "numeric argument".

When type is :menu, this item indicates that a sub-menu will be invoked, and so value must be
another command table or the name of another command table.

When type is :divider, some sort of a dividing line is displayed in the menu at that point. If
string is supplied, it will be drawn as the divider instead of a line. If the look and feel provided by
the underlying window system has no corresponding concept, :divider items may be ignored.
value is ignored.

documentation is a documentation string, which can be used as mouse documentation for the
command menu item.