This should't change behavior in practice since using these in constants
doesn't seem possible.

Closes #850

Signed-off-by: Marin Veršić <[email protected]>

Since Cython 3.0 using dots appart from the extension is
a hard error. See issue: cython/cython#2686

Cython 3.0 deprecated `IF` and `DEF`. Until this is fixed
allow warnings in our `Cython` tests.
Background: cython/cython#4310

Note the warnings will become hard errors in the future.

Rename expectation files to contain only one dot.
This is needed for the Cython tests as of Cython 3.
The following script was used in a clean repository
to rename the files:

```sh
 ls | sed -E -n 's/(.*)\.(both|tag)?((\..*)?\.(c|cpp|pyx))/mv "\1.\2\3" "\1_\2\3"/p' | sh
```

I forgot forcing stable rustc for semver-checks in commit 67fea1a.
On nightly Rust it is possible for the rustdoc version
to be newer than what cargo semver checks supports.

Closes #864

Closes #875.
Closes #860.
Closes #408.

the msrv was bumped in in the Cargo.toml #847 but not in clippy.toml,
clippy was complaining at startup and defaulting to 1.57

 * Fix swapping of `>>=` and `<<=` in constants.
 * Add support for #[deprecated] (#860).
 * Built-in support for bitflags 2.0.
 * Support for "C-unwind" ABI.
 * Generate bindings for non-public extern items if they are #[no_mangle].