fix B14012 - polymorph of monster possessions

Forwarded from the newsgroup:  when a monster gets hit by wand or
spell of polymorph, any armor that fell off was protected from being
hit by that same zap, but a dropped weapon wasn't.  Nor was the whole
dropped inventory in the case where the monster is killed by system
shock rather than transformed.  Protect its entire inventory.

src/bones.c

@@ -201,6 +201,7 @@ struct obj *corpse;
 
 	/* caller has already checked `can_make_bones()' */
 
+	clear_bypasses();
 	fd = open_bonesfile(&u.uz, &bonesid);
 	if (fd >= 0) {
 		(void) close(fd);