GETEXITNUM (number)
        
   Synopsis:
      Returns the exit model number of an exit in the automapper's current room

   Notes:
      'number' is the position of the exit in the room's ordered list of exits
         (the first exit is numbered 1).
      If there is no current room or if the numbered exit doesn't exist, returns 
         0.
      To get the number of exits in the current room, see the GETROOMEXITS
         function.
