Get rid of ATTR_DELAY_SWAP_INTERRUPTED and all its attendant code.

These days, the only time a player was likely to run into it was when
transforming while wielding a non-weapon. Then, it gave an annoying prompt
asking you whether you wanted to swap back to your main weapon when the
transform ended, even though it switched to a non-weapon and most likely
your "main weapon" was your bare fists, if you were casting form spells.

The only other case where it would matter is casting lichform while
wielding a holy weapon. I hope players who do this won't be bothered by
having to switch back manually.
Move butchery() from food.cc to butcher.cc.

I promise this is totally related to the rest of this branch!