Explore using more traditional grammars for parsing

[patrickt]

Combining the semantic and parsing steps is, I think, just too difficult. (Fiddly at the very least.) Perhaps we should explore moving away from parser combinators and towards a more formal and well-tested grammar system. We could pull in ANTLR or Language.C and have the translation to a semantic tree be a separate step. We probably won't find a parser that operates on fixpoints of functors, but we can do some automated translations with GHC generics or Uniplate.