B01001 fix: corpse grammar

<Someone> wrote:
> You start bashing monsters with your 2 cockatrice corpses.
> You hit the foo with the cockatrice corpse (note singular).
> The foo is slowing down. The foo turns to stone.
> Also: Your cockatrice corpses rots away.

It appears that vtense() has a problem recognizing "corpses"
as plural.  This doesn't fix that, it just switches to using
otense() in this particular case.

src/dig.c

@@ -1538,7 +1538,7 @@ long timeout;	/* unused */
 		char *cname = corpse_xname(obj, FALSE);
 		Your("%s%s %s away%c",
 		     obj == uwep ? "wielded " : nul, cname,
-		     vtense(cname, "rot"), obj == uwep ? '!' : '.');
+		     otense(obj, "rot"), obj == uwep ? '!' : '.');
 	    }
 	    if (obj == uwep) {
 		uwepgone();	/* now bare handed */