XPappendThere()
   Report whether APPEND is installed.
------------------------------------------------------------------------------

   Function:   XPappendThere()

               Reports whether DOS' APPEND.COM has been installed.
               Then one can use XPappendPath() to inspect APPEND's PATH.
               This feature only works for DOS versions higher than
               DOS 3.30 if I'm well informed.

   Syntax:     XPappendThere() --> lAppend

   Arguments:  None

   Returns:    A logical, true if APPEND is installed.

   Usage:      if !XPappendThere()
                    ? 'Hey Dumbo, where can I look for those bloody'
                    ? 'files I currently cannot find?'
               Endif