This class implements a menu with callback-based menu items and keyboard equivalents. Menus from this class should only be used with menu bars from mred:menu-bar%.
Uses dispatch as the default func.
If the title argument is not null, it is be used when the menu is used as a pop-up menu on some platforms. If func is not null, it will be called when the user selects an item by a call to popup-menu or popup-menu.