Hello, I've merged the main part of PEP-652 implementation. The Limited C API (introduced in PEP 384 and used for extension modules that work across Python versions without recompilation) is now explicitly defined and better tested.

When changing/extending the limited API: - Stop and think! This API will need to be suppported forever (or until Python 3 reaches end of life, if that comes sooner). A checklist of what to think about is being added to the devguide [0]. - Add/change an entry in `Misc/stable_abi.txt`. - Run `make regen-limited-abi` [sic].

You can run related checks with `make check-limited-abi`. If that or the "Check if generated files are up to date" CI test gives you errors, please let me know!

More tests & docs are coming up.

[0]: https://cpython-devguide--682.org.readthedocs.build/c-api/