The compiler middle stage takes high level nodes and produces code in
an intermediate representation more closely resembling assembly code.
Optimizations and the tools for making those are also included. It's
significantly easier to optimize IR than syntax trees or assembly.
Several things need cleaning up, in particular there are things in
jigs.lisp that really should be documented tools, not
jigs (specifically the compilation setup and finalization).
It ingests tokens via a "token stream", and feeds out a node
tree. It's a mostly handwritten recursive descent parser with the
occasional Lisp macros for convenience.
