Restore basic language builtins

I regret removing these in the beginning.  It shouldn't break anything to add them back and it will make life easier for people coming from the lua side who are used to them being globals.

I am still leaving out things like `os`, `io`, `loadfile`, and `dofile` because they easily do process blocking I/O killing luvit performance.
The debug line is actually not a change, notice we override it a few lines later.