- Reformat the C API and ABI Versioning page (and extend/clarify a bit)
- Rewrite the stable ABI docs into a general text on C API Compatibility
- Add a list of Limited API contents, and notes for the individual items.
- Replace `Include/README.rst` with a link to a devguide page with the same info
Fixed some errors in refcounts.dat, remove functions removed in
Python 3, and add more entries for documented functions. This will
add several automatically generated notes about return values.