REVPATH variable-name

   Synopsis:
      Attempts to reverse a list of direction

   Notes:
      The variable should be an array containing the series of commands to be 
         sent to the world in order to travel between two locations, e.g.
         
            "north", "northwest", "up", "east"
            
      REVPATH attempts to use Axmud's path-reversal functions to produce a list
          of commands for travelling in the opposite direction, e.g.
          
            "west", "down", "southeast", "south"
            
      If the current dictonary doesn't know the opposite of a particular
         direction, that direction remains unchanged, e.g.
         
            "north", "perambulate", "west"
               >> "east", "perambulate", "south"
               
      If the array is empty, no error message is generated: the array remains
         unmodified. REVPATH assumes that the array starts at element #1.

   Examples:
      DATA "north", "northwest", "up", "east"
      DIM myarray$ (4)
      FOR a = 1 TO 4
         READ myarray$ (a)
      NEXT a

      REVPATH myarray$
      FOR a = 1 TO 4
         PRINT myarray$ (a)
      NEXT a
