These commits take the old bitv implementation and modernize it with an explicit self, some minor touchups, and using what I think is some more recent patterns (like `::new` instead of `Type()`).
Additionally, this adds an implementation of `container::Set` on top of a bit vector to have as a set of `uint`s. I initially tried to parameterize the type for the set to be `T: NumCast` but I was hitting build problems in stage0 which I think means that it's not in a snapshot yet, so it's just hardcoded as a set of `uint`s now. In the future perhaps it could be parameterized. I'm not sure if it would really add anything, though, so maybe it's nicer to be hardcoded anyway.
I also added some extra methods to do normal bit vector operations on the set in-place, but these aren't a part of the `Set` trait right now. I haven't benchmarked any of these operations just yet, but I imagine that there's quite a lot of room for optimization here and there.
r?
Apply deriving_eq to the data structures in ast.rs, and get rid of the custom definitions of eq that were everywhere. resulting ast.rs is about 400 lines shorter.
Also: add a few test cases and a bunch of comments.
Also: change ast_ty_to_ty_cache to use node ids rather than ast::ty's. I believe this was a suggestion related to my changes, and it appears to pass all tests.
Also: tiny doc fix, remove references to crate keywords.
r?
I added code to the JSON encoder to support the serialization of enums. Before this, the JSON serializer only handled Option, and encoded None as 'null'. Following this change, all enums are encoded as arrays containing the enum name followed by the encoded fields. This appears consistent with the unstated invariant that the resulting output can be mapped back to the input *if* there's a decoder around that knows the types that were in existence when the serialization occurred.
Also, added test cases.
