Ishiddenexit (number)

   Synopsis:
      Tests whether an exit is hidden

   Notes:
      'Hidden' exits exist in the world, but are not always visible in the room
         description. A idden exit is always visible in Axmud's automapper
         window.

      Returns 1 if the exit is hidden. Returns 0 if the exit is not hidden, or
         if the specified exit doesn't exist.
