fix github issue #349 - out of depth liches

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

doc/fixes37.0

@@ -1,4 +1,4 @@
-$NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.223 $ $NHDT-Date: 1589827569 2020/05/18 18:46:09 $
+$NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.225 $ $NHDT-Date: 1590613502 2020/05/27 21:05:02 $
 
 General Fixes and Modified Features
 -----------------------------------
@@ -187,6 +187,9 @@ hold_another_object used hardcoded Stressed to limit carrying instead of
 	using the 'pickup_burden' option for that
 when hold_another_object fails while hero is swallowed, drop the item into
 	swallower's inventory instead of onto the floor
+change mkclass() to usually honor (always honor for L class) the hell-only and
+	never-in-hell monster creation flags; no more achi-lich in the Castle
+	(nor master lich there unless demilich gets a potion of gain level)
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

src/makemon.c

@@ -1,4 +1,4 @@
-/* NetHack 3.6	makemon.c	$NHDT-Date: 1587024537 2020/04/16 08:08:57 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.168 $ */
+/* NetHack 3.6	makemon.c	$NHDT-Date: 1590613502 2020/05/27 21:05:02 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.170 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2012. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -1663,8 +1663,7 @@ aligntyp atyp;
 {
     register int first, last, num = 0;
     int k, nums[SPECIAL_PM + 1]; /* +1: insurance for final return value */
-    int ignore = (spc & G_IGNORE);
+    int maxmlev, gmask;
-    int maxmlev, mask = (G_NOGEN | G_UNIQ) & ~spc;
 
     (void) memset((genericptr_t) nums, 0, sizeof nums);
     maxmlev = level_difficulty() >> 1;
@@ -1686,13 +1685,24 @@ aligntyp atyp;
         return (struct permonst *) 0;
     }
 
+    gmask = (G_NOGEN | G_UNIQ);
+    /* traditionally mkclass() ignored hell-only and never-in-hell;
+       now we usually honor those but not all the time, mostly so that
+       the majority of major demons aren't constrained to Gehennom;
+       arch- and master liches are always so constrained (for creation;
+       lesser liches might grow up into them elsewhere) */
+    if (rn2(9) || class == S_LICH)
+        gmask |= (Inhell ? G_NOHELL : G_HELL);
+    gmask &= ~spc;
+    gmask |= (spc & G_IGNORE);
+
     /*  Assumption #2:  monsters of a given class are presented in ascending
      *                  order of strength.
      */
     for (last = first; last < SPECIAL_PM && mons[last].mlet == class; last++) {
         if (atyp != A_NONE && sgn(mons[last].maligntyp) != sgn(atyp))
             continue;
-        if (mk_gen_ok(last, G_GONE, mask|ignore)) {
+        if (mk_gen_ok(last, G_GONE, gmask)) {
             /* consider it; don't reject a toostrong() monster if we
                don't have anything yet (num==0) or if it is the same
                (or lower) difficulty as preceding candidate (non-zero
@@ -1738,6 +1748,7 @@ mkclass_poly(class)
 int class;
 {
     register int first, last, num = 0;
+    int gmask;
 
     for (first = LOW_PM; first < SPECIAL_PM; first++)
         if (mons[first].mlet == class)
@@ -1745,14 +1756,18 @@ int class;
     if (first == SPECIAL_PM)
         return NON_PM;
 
+    gmask = (G_NOGEN | G_UNIQ);
+    if (rn2(9) || class == S_LICH)
+        gmask |= (Inhell ? G_NOHELL : G_HELL);
+
     for (last = first; last < SPECIAL_PM && mons[last].mlet == class; last++)
-        if (mk_gen_ok(last, G_GENOD, (G_NOGEN | G_UNIQ)))
+        if (mk_gen_ok(last, G_GENOD, gmask))
             num += mons[last].geno & G_FREQ;
     if (!num)
         return NON_PM;
 
     for (num = rnd(num); num > 0; first++)
-        if (mk_gen_ok(first, G_GENOD, (G_NOGEN | G_UNIQ)))
+        if (mk_gen_ok(first, G_GENOD, gmask))
             num -= mons[first].geno & G_FREQ;
     first--; /* correct an off-by-one error */