github issue #935 - disarming swallowed hero

Issue reported by AndrioCelos:  bullwhip using monster was able to
snatch hero's weapon when hero was engulfed.

Fix is trivial:  when a monster is choosing an item to use, don't
pick bullwhip if hero is engulfed.  Regular attack attempts already
skip engulfed hero.

Fixes #935

src/muse.c

@@ -1963,6 +1963,7 @@ find_misc(struct monst* mtmp)
             && next2u(mtmp->mx, mtmp->my)
             /* don't bother if it can't work (this doesn't
                prevent cursed weapons from being targeted) */
+            && !u.uswallow
             && (canletgo(uwep, "")
                 || (u.twoweap && canletgo(uswapwep, "")))) {
             g.m.misc = obj;