rust-cpython: remove PySharedRefCell and its companion structs
Also updates py_shared_iterator!() documentation accordingly.
rust-cpython: switch to upstreamed version of PySharedRefCell
Our PyLeaked is identical to cpython::UnsafePyLeaked. I've renamed it because
it provides mostly unsafe functions.
rust-cpython: rename inner_shared() to inner()
The "shared" accessor will be automatically generated, and will have the
same name as the data itself.
rust-cpython: use PyList.insert() instead of .insert_item()
Silences the deprecated warning.
https://github.com/dgrunwald/rust-cpython/commit/
e8cbe864841714c5555db8c90e057bd11e360c7f