Define missing import APIs

[indygreg]

I need some of these APIs for the pyembed crate (used as part of
PyOxidizer). I figured I might as well define them all.

All these APIs are limited.

I don't have a PyPy install with a shared library to test. We may need to disable these when targeting PyPy.

[davidhewitt]

Thanks for adding these. Can they please be located in src/ffi/cpython/import.rs?

We try to match the cpython header structure as much as possible to make it easier to diff against upstream changes.

If you're willing to put the definitions as the same order as they currently are in the cpython header, that'd also be much appreciated.

[davidhewitt]

This extern block contains pub static mut so it's going to need #[cfg_attr(windows, link(name = "pythonXY"))]

[davidhewitt]

Also can confirm that none of these APIs appear to exist for PyPy.

[kngwyu]

Thanks. As David says, please consider placing some APIs in cpython mod. We're refactoring the FFI module in that way (#1289).

[indygreg]

For some reason I'm getting a compiler warning about PyImport_ExtendInittab() being unused, so I suppressed this. Unsure why. Maybe the presence of the pub static mut above triggers it?

[indygreg]

Yeah, that was it. I moved this to its own block 🤷‍♂️

[davidhewitt]

Thanks! Just a final couple of tweaks needed before merging.

Strange, I can't reproduce the unused code warning if I remove those two attributes from the static mut variables...

[nw0]

I think the current comments cover everything in import.h from CPython master.

[davidhewitt]

@indygreg thanks for pushing this PR along to this point; I'm going to take it over and push a commit shortly to finish it off as part of some tidy-ups I'm doing for the 0.14 release.