Moving right along... start on the analyzer-in-Tamsin.

--HG--
rename : eg/tamsin-desugarer.tamsin => lib/tamsin_analyzer.tamsin
Slot for locals in the production(...) term.
Production-linking is now part of desugaring.
Just need to get reverse_prod() working...
Maaan... nuts to this, I'm gonna refactor the AST.
Add ProdBranch AST node.  Interpreter passes.
Compiler has some problems with branches, but only 9 failures.
Fix up compiler.
Catch-up implementation in Tamsin.  All tests pass.
Analyzer in Tamsin resolves module names.  It's a step.
Going to need to extend the AST to cover all parts of a Term...
ASTs no longer contain Terms.  But they can be turned into them.
Catch up Tamsin impl.  It DOES collect locals, but order differs.