Update cbindgen requirement from 0.20 to 0.23

[dependabot]

Updates the requirements on cbindgen to permit the latest version.

Release notes

Sourced from cbindgen's releases.

v0.23.0

• Better support for constexpr. (#756)
• constexpr is now enabled by default in C++ mode. You can use const.allow_constexpr=false to revert to previous behavior. (#756)
• Minimum syn version no longer parses old rust code. (#754)

Changelog

Sourced from cbindgen's changelog.

0.23.0

  * Better support for constexpr. ([#756](https://github.com/eqrion/cbindgen/issues/756))
  * constexpr is now enabled by default in C++ mode. You can use const.allow_constexpr=false to revert to previous behavior. ([#756](https://github.com/eqrion/cbindgen/issues/756))
  * Minimum syn version no longer parses old rust code. ([#754](https://github.com/eqrion/cbindgen/issues/754))

0.22.0

  * Support rename rule for union body members ([#751](https://github.com/eqrion/cbindgen/issues/751)).
  * constant: Add support for associated constant expressions ([#752](https://github.com/eqrion/cbindgen/issues/752)).
  * Fix regression in CamelCase rename rule (should be lowerCamelCase) ([#750](https://github.com/eqrion/cbindgen/issues/750)).
  * enumeration: simplify standard types in variants ([#749](https://github.com/eqrion/cbindgen/issues/749)).
  * Avoid generating and writing bindings when called recursively ([#747](https://github.com/eqrion/cbindgen/issues/747)).
  * Cython: Omit per-variant tags in unions generated for Rust enums ([#748](https://github.com/eqrion/cbindgen/issues/748)).
  * Update various dependencies.

0.21.0

  * Update MSRV to 1.54.0
  * Update clap to 3.1.
  * Update heck to 0.4.0
  * unraw identifiers
  * Honor documentation_length in Cython.
  * Add documentation_style to with short and full options
  * Map RawFd to Int
  * Respect remove_underscores config when prefixing name to enum

0.20.0

 * Add Builder::with_using_namespaces. ([#688](https://github.com/eqrion/cbindgen/issues/688))
 * Ignore PhantomPinned. ([#695](https://github.com/eqrion/cbindgen/issues/695))
 * Simplify Pin<T> to T. ([#697](https://github.com/eqrion/cbindgen/issues/697))
 * Update --pretty=expanded to -Zunpretty=expanded. ([#706](https://github.com/eqrion/cbindgen/issues/706))

0.19.0

 * Simplify types in generics ([#663](https://github.com/eqrion/cbindgen/issues/663))
 * Use --profile=check for macro expansion ([#671](https://github.com/eqrion/cbindgen/issues/671))
 * Use exported name to prefix enum variants ([#672](https://github.com/eqrion/cbindgen/issues/672))
 * Fix path attribute handling in inline submodules ([#679](https://github.com/eqrion/cbindgen/issues/679))
 * Fix a stack overflow with some recursive typedefs ([#680](https://github.com/eqrion/cbindgen/issues/680))

0.18.0

 * Simplify types in nested types such as pointed-to types and function signatures ([#661](https://github.com/eqrion/cbindgen/issues/661))

0.17.0

 * Add with_parse_extra_bindings to builder. ([#645](https://github.com/eqrion/cbindgen/issues/645))
 * Support NonZero and fix incorrect simplification of Option<ptr> into ptr. ([#647](https://github.com/eqrion/cbindgen/issues/647))

... (truncated)

Commits

• 798cfab v0.23.0
• 305ccfe constant: Make const.allow_constexpr default to true.
• 15e1131 constant: Allow more constexpr constants.
• a0ab624 Update syn dependency to at least 1.0.88
• 8cfd457 Fix #753
• 8604b2c v0.22.0
• 5b418d9 Support rename rule for union body members.
• 770f352 constant: Add support for other expressions WebRender uses.
• 882af0b constant: Add support for associated constant expressions.
• 20ddfff Fix regression in CamelCase rename rule (should be lowerCamelCase)
• Additional commits viewable in compare view

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[dependabot]

Superseded by #34.