Loop fusion passes

[hansihe]

Work on passes that fuse "loops" (for, Enum functions) in order to improve analyzability.

[hansihe]

One option here is to "cheat" using the process dictionary to implement accumulators/mappers. This would make it possible for us to do a much wider range of stuff without having to shoehorn the inherently arbitrary control flow into more standard constructs.

We would still present the illusion of everything being just as normal.