Type information for faster Python C extensions

This is really clever. I was surprised at how much speedup they got by just adding type information. But also the trick to make it ABI compatible with the current API. Takes a certain amount of madness.

I think the GraalVM approach of transforming the C into your own IR and then JITing that is another interesting approach. Essentially treat Java and C as one unified source and compile them together. That certainly takes more work and a very expressive IR, but it is another way to deal with the inefficiency at the API boundary.