Debug entity upvalue

So it turns out arrows have lurking upvalues...

I rewrote table.check so it gives more information and can be passed a do_recurse function. (So I could actually find the upvalues).
I gave talents and talent-types a __CLASSNAME field so they're not treated as tables to be copied. (And so aren't checked for upvalues).
A projectile's "def" table now has an _allow_upvalue flag, to account for the "block" upvalue that's already accounted for in the code.

Simple bugfixes

If you're pinned, a swap with a friendly still takes energy.

Was going to outright disable it, but doctornull talked me out of it?

Debug entity upvalue

Moves the upvalue checker into Entity:init, so that entities created by talents and such get run through it as well.

Callbacks now work for items too, they trigger by default when worn, but an be forced to trigger even when not by setting carrier_callbacks = true on the item

Races can define "_forbid_start_override" to not be subjected to archmages/chronomancers/.. different starting zones

Mindslayer corrections

That should fix up all the issues now.

Well, except for the lack of decent equipment. :P