Added a new smarter optimizer.

[Idorobots]

Refs #153

It's also way slower...

• pmap different optimization runs to make this a bit faster. Futures block immediately, places won't allow sending the AST and threads are just as slow as sequential, since Racket doesn't support proper OS threads.
• Tweak the estimate-perf to produce better code.
• Add a third "complexity" measure so that it prefers less complex code.
• Add a fourth "further optimization potential" measure.
• Figure out how to treat self-recursive functions, so that we can optimize factorial away.
• Run optimizations lazily and incrementally, so that there's no need to inline functions in a branch that is dead.