Add tools to ensure we didn't break API compatibility #22
Description
Now that we're better about making sure everything has a unique reference in Ares, we need to be sure that we don't accidentally remove anything from the API surface, and adding anything should increment the API version. We need some tooling to ensure that we do so. Might also be nice to be able to swap out function implementations depending on API version if necessary to help us avoid the ll.*Base64.*Correct() problem.