B01001 fix: corpse grammar

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.