XPpullInit()
 Initialise the Pull Down Menu system
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   Function:   XPpullInit()

               This function initialises the Pull down menu System, as
               used by the XPDEMO program for instance. This is needed
               for speed, so quite some settings can de preset, so that
               calling XPpullMenu() does not require rearranging all kinds
               of settings.

               XPpullInit() accepts an Array describing the Menu. See below
               for it's format (quite extensive).

               This function's parameters are quite complicated. Therefore,
               the best way to know how to use them would be to inspect
               the XPDEMO program, which demos how to make a menu System.

   Syntax:     XPpullInit(aMenu,bMsg)

   Arguments:  aMenu is the Pulldown system Array, see XPDEMO program
               for details. bMsg is the code-Block to invoke for messages.

   Returns:    NIL

   Usage:      See XPDEMO.