These are just some notes I'm making for myself in the
course of getting familiar with the code.  If you are
not me, you can ignore them.

Level Stuff:
 * Key files include
   mklev.c
   sp_lev.c
   dungeon.c
   mkmaze.c
   mkroom.c
 * Still figuring out the relationship between
   add_room/add_subroom versus makerooms/create_room
 * makelevel notices if there haven't been any levels
   created already (based on wiz1_level.dlevel) and 
   in that case calls init_dungeons() before proceeding.
 * makelevel calls oinit(lev), which currently only
   sets the level-dependent probabilities for the 
   various gemstones.  Could this also be made to 
   adjust object probabilities per branch?
 * The second argument to makemaz is "minefill" when
   creating Mines filler levels (caverns).  Other possible
   values include the empty string (used in Gehennom among
   other places) and, umm, maybe some other possibilities.
   (If I read the code in makelevel correctly, each quest
   has its own value, and the rogue level may have another.)
 * makelevel (in mklev.c) appears to be the key level-making
   function.  It does one of three things:
   + calls makemaz and returns; makemaz must do everything
   + calls makeroguerooms and sort_rooms, does stair
     placement, then skips down and does branch placement,
     puts things in the rooms (monsters, traps, random objects).
   + calls makerooms and sort_rooms, does stair placement,
     calls makecorridors and make_niches, possibly creates a
     vault, maybe turns some of the rooms into special rooms
     (shops, throne rooms, leprechaun halls, zoos, temples,
     beehives, gravehards, antholes, barracks, swamps, or
     cockatrice nests), does branch placement, puts things
     in the rooms  (monsters, traps, fountains, sinks,
     altars, graves, statues, boxes/chests, graffiti, and
     random objects).
   HOWEVER, makelevel does not do everything.  It is itself
   called by mklev, which also does some other stuff, e.g.,
   mklev calls mineralize and set_wall_state.  Also, it is
   mklevl that decides whether to load bones or create a
   level from scratch, apparently.
 * In addition to gold and gems, mineralize also places
   kelp.  It would be a logical place for inserting other
   similar things: rocks, for example.
 * topologize sets the room number on every tile in a
   room to be that room's number.  In light of this, I'm
   not sure why pos_to_room is necessary.