Have monsters' hole destination match the hero's

The fixed destination of a hole or trap door was being used for the hero
but not for monsters.  Make everyone land in the same place, so you can
chase a monster into a hole and actually find it.

src/teleport.c

@@ -1539,7 +1539,7 @@ mlevel_tele_trap(
                           (tt == HOLE) ? "hole" : "trap");
                 return Trap_Effect_Finished;
             } else {
-                get_level(&tolevel, depth(&u.uz) + 1);
+                assign_level(&tolevel, &trap->dst);
             }
         } else if (tt == MAGIC_PORTAL) {
             if (In_endgame(&u.uz) && (mon_has_amulet(mtmp)