Change mkclass() to always honor the hell-only monster generation
flag for L class, preventing master and arch-liches outside Gehennom.
For other classes, honor hell-only and outside-hell-only most (89%)
of the time. When not honored (11%), it allows demons and devils to
appear outside of Gehennom as they have in the past. [That part
might need to be re-done since it is done for all monsters in the
class on any mkclass() call instead of being done on a class-member
by class-member basis within each such call.]
This prevents out of depth liches in the Castle and ought to do same
for themed rooms of type 'Mausoleum' although I haven't figured out
how to test that.
Fixes#349
c29ffe1d82