NAME
        OnMenu -- enable the given menu or menu item.
    SYNOPSIS
        OnMenu( window, menunumber )
                A0      D0
        VOID OnMenu( struct window *, uword );
    FUNCTION
        This command enables a sub-item, an item, or a whole menu.
        This depends on the contents of the data packed into MenuNumber,
        which is described in the Intuition Reference Manual.
    INPUTS
        window = pointer to the window
        MenuNumber = the menu piece to be enables
    RESULT
        None
    BUGS
    SEE ALSO
        offmenu(), resetmenustrip()