SET-MENU-ITEM-SENSITIVITY
=========================

syntax: (set-menu-item-sensitivity 
           <babylon-menu-item> <T | NIL>)

This function indicates, whether the menu-item is
sensitive or not. NIL indicates that the menu-item is 
insensitive.

example: >(set-menu-item-sensitivity
             (get-babylon-menu-item interface
             "MENU1" "MENU-ITEM1")
             NIL)