Compiler cleanups

I started digging into the relooper and decided to do some cleanups as I go along. @mbebenita, it'd be great if you could give these a look-over.

Also, I'd love to have a chat about `bytecode.ts` and `looper.ts` and the duplication between the two. Both in terms of source code and, to my understanding, in terms of passes applied to the processed content. Clearly, there are gaping holes in my understanding, and I'l like to at least somewhat fix that.