THRIFT-4529: Rust enum variants are now camel-cased

[allengeorge]

Client: rs

[allengeorge]

Build failure caused by a PEBCAK on my part (forgot to change enum variant names in cross-tests). Fixing now.

[jeking3]

I assume the default setting is to use the previous way, and this is a new way, so it is backwards compatible?

[allengeorge]

I did not include a flag for backwards-compatibility. I'd prefer not to, because this change makes the autogenerated code conform to Rust naming conventions.

[jeking3]

This is a breaking change based on the conversation. That means it needs a lib/rs/README.md entry indicating such, and an entry in the top level CHANGES file in the appropriate section for breaking changes.

[allengeorge]

Yes - you're right: it is a breaking change. I'll make the README entries, and make sure I do so for any (hopefully rare!) breaking changes I make in the future. Thank you for catching this.

[allengeorge]

I've updated the CHANGES file, plus added a Compatibility section to the Rust README along with transition guidelines. I will do this in the future for any breaking changes.

[allengeorge]

@jeking3 I've made the requested changes, and, the only thing that fails in Travis is the SBCL build under autotools :/ Could this be merged please?