fix bug in mon.c reported by paxed

Also adds a shorthand macro
    monsym(&mons[n])
for getting the default symbol, used in the bugfix.

include/mondata.h

@@ -260,5 +260,6 @@
 #define pmname(ptr,g) ((((g) == MALE || (g) == FEMALE) && (ptr)->pmnames[g]) \
                         ? (ptr)->pmnames[g] : (ptr)->pmnames[NEUTRAL])
 #endif
+#define monsym(ptr) (def_monsyms[(int) (ptr)->mlet].sym)
 
 #endif /* MONDATA_H */

src/detect.c

@@ -106,7 +106,7 @@ browse_map(unsigned ter_typ, const char *ter_explain)
 static void
 map_monst(struct monst *mtmp, boolean showtail)
 {
-    int glyph = (def_monsyms[(int) mtmp->data->mlet].sym == ' ')
+    int glyph = (monsym(mtmp->data) == ' ')
                 ? detected_mon_to_glyph(mtmp, newsym_rn2)
                 : mtmp->mtame
                   ? pet_to_glyph(mtmp, newsym_rn2)

src/makemon.c

@@ -1640,7 +1640,7 @@ rndmonst_adj(int minadj, int maxadj)
 
         if (montooweak(mndx, minmlev) || montoostrong(mndx, maxmlev))
             continue;
-        if (upper && !isupper((uchar) def_monsyms[(int) ptr->mlet].sym))
+        if (upper && !isupper(monsym(ptr)))
             continue;
         if (elemlevel && wrong_elem_type(ptr))
             continue;

src/mon.c

@@ -4419,7 +4419,7 @@ pick_animal(void)
     /* rogue level should use monsters represented by uppercase letters
        only, but since chameleons aren't generated there (not uppercase!)
        we don't perform a lot of retries */
-    if (Is_rogue_level(&u.uz) && !isupper((uchar) mons[res].mlet))
+    if (Is_rogue_level(&u.uz) && !isupper(monsym(&mons[res])))
         res = ga.animal_list[rn2(ga.animal_list_count)];
     return res;
 }

src/sp_lev.c

@@ -3306,7 +3306,7 @@ lspo_monster(lua_State *L)
         tmpmons.coord = SP_COORD_PACK(mx, my);
 
     if (tmpmons.id != NON_PM && tmpmons.class == -1)
-        tmpmons.class = def_monsyms[(int) mons[tmpmons.id].mlet].sym;
+        tmpmons.class = monsym(&mons[tmpmons.id]);
 
     create_monster(&tmpmons, gc.coder->croom);