Generate a menu of choices for user input.

  K = MENU('Choose a color','Red','Blue','Green') displays on

  the screen:



  ----- Choose a color -----



     1) Red

     2) Blue

     3) Green



     Select a menu number: 



  The number entered by the user in response to the prompt is

  returned.  On machines that support it, the local menu system

  is used.  The maximum number of menu items is 32.