revamp baalz level

Quite a bit of special case code for something so inconsequential.
Tweak the baalz level layout a little to make it be a bit more
interesting, and perform custom wallification on it so that the
beetle layout becomes clearly visible.  It looks great with
DECgraphics (and presumably IBMgraphics).  It's recognizeable but
not as interesting with ordinary ascii because corner walls use
'-' or '|' so don't join up nicely.  It looks a little weird
with tiles; the square aspect ratio of individual tiles makes it
end up being very elongated compared to character cell map it was
designed for.

As far as the level layout goes, the pair of secret doors into
Baalzebub's chamber have been give a random alternative.  The two
right-most accessible columns were diggable--I don't know whether
that was intentional; it's been reduced to one right-most column.
The middle pair of legs were asymmetrical; this fixes that.  The
beetle also now has eyes and an entry door in its mouth.

doc/fixes36.1

@@ -197,6 +197,7 @@ when using the 'O' command for regexp options (autopickup exceptions,
 	at a time [after 'add', return to add/list/remove menu]
 commands invoked by uppercase meta characters: M-A, M-C, M-N, M-O, M-R, M-T
 	were missing from '? c' list of game commands (dat/hh)
+tweak Baalzebub's lair and clean up the map display for it
 
 post-3.6.0: fix "object lost" panic during pickup caused by sortloot revamp
 post-3.6.0: more sortloot revisions