get-shortcut in selectable-menu-item<%>
Gets the keyboard shortcut character for the menu item. Under
Mac OS, this character is always prefixed with the command
modifier. Under Windows, the character is prefixed with the control
modifier. Under X, the modifier depends on the shortcut prefix
returned by
get-x-shortcut-prefix.
If the menu item has no shortcut, #f is returned.
The shortcut part of a menu item name is not included in the label
returned by
get-label.