Still needs a LOT of testing. It's probably pretty broken right now.

Also fixed how environments are injected (I think?). Still generates 5.1 bytecode, so that'll have to be switched to 5.2.

I had to revert the changes to the code generator back to pure 5.1, so
_ENV is no longer special in code. However, the environment is still
stored as an upvalue, even on 5.1 (which is the version the bytecode
is generated for). It properly loads 5.2 bytecode for the most part, but
there's still a few things broken with upvalues. (It's able to get CC
to partially boot through the BIOS!)

Boots CraftOS! (when precompiled to 5.2)
Now to write the compiler...

This is complete enough to fully boot CraftOS in
Lua 5.2; no precompilation necessary.

This should theoretically be the last thing to implement.
I think there's also something with weak tables to fix,
as well as adding tail call hooks, but those are much
more minor details.

If you don't like goto, you can disable it with
LuaC.blockGoto.

Also fixed some bugs that made the tests fail.

goto can now be used as a variable name again, for old
programs that used it. (Don't do this anymore.)

(read: `goto = 2` works)

Also fixed a bunch of stuff to make CC tests pass.

There's still a couple more to finish before it'll pass.

I had to delete any lines that used varargs, as Cobalt
provides Lua 5.0-style arg tables, which does not exist in
any form under Lua 5.2. Maybe this should be refactored/
adjusted so vararg compilation can be properly tested?

Now, when blockGoto is enabled, goto is always treated as a name instead of throwing an error. This is much more useful than the previous behavior.