Addexit (number, string)
Addexit (number, string, string)

   Synopsis:
      Adds a new exit to the exit model

   Notes:
      'room_num' is the number of the room, to which the exit will be added.
      The two string arguments specify a direction. The first is the exit's
         actual direction, such as "north", "up" or "out".
      The second represents the primary direction in which the exit is drawn
         on the map. For example, to add an "out" exit to room 2, drawn in the
         northerly direction:

         Addexit(2, "out", "north")

      In this situation, if you don't specify a primary direction, Axbasic will
         choose the first available one (which might be "north"):

         Addexit(2, "out")

      If the exit is actually a north exit, then you don't need to specify both
         strings:

         Addexit(2, "north")

      If the operation is successful, the new exit's exit model number is
         returned. If the operation fails, 0 is returned.
