Expand on the C api definitions

[mejrs]

I'm not entirely sure whether I got the cfg's right. When do I need to add (or not add) a PyPy gate?

[davidhewitt]

Nice, these changes look along the right lines to me! It would be nice to add some tests for the inlined functions in methodobject.rs

I'm not entirely sure whether I got the cfg's right. When do I need to add (or not add) a PyPy gate?

TBH I think struct definitions should be checked carefully whether they're PyPy compatible, because we could get UB/crashes if they're wrong. For functions, the worst that happens is that we get a linker error if there's a PyPy gate missing. So I tend to be a bit lax with PyPy gates on functions, though in principle they all could have either a not(PyPy) or a link_name = "PyPy..." attribute.

[mejrs]

I think that's all. I can't quite figure out how to squash them though. I suppose we can "squash and merge"?

[davidhewitt]

👍 looks good to me, I'll click squash & merge. Thanks! (Hopefully with this PR pyo3-ffi-check will now be happy for 3.11.)