Update cbindgen requirement from ^0.13 to ^0.20

[dependabot-preview]

Updates the requirements on cbindgen to permit the latest version.

Release notes

Sourced from cbindgen's releases.

v0.20.0

• Add Builder::with_using_namespaces. (#688)
• Ignore PhantomPinned. (#695)
• Simplify Pin to T. (#697)
• Update --pretty=expanded to -Zunpretty=expanded. (#706)

Changelog

Sourced from cbindgen's changelog.

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))
 * Deal with name conflicts correctly in declaration type resolution. ([#651](https://github.com/eqrion/cbindgen/issues/651))
 * Support pointers to ZSTs. ([#656](https://github.com/eqrion/cbindgen/issues/656))

0.16.0

 * Remove artificial restriction on lifetime parameters on enums ([#604](https://github.com/eqrion/cbindgen/issues/604))
 * Add an option for converting usize/isize into size_t/ptrdiff_t. ([#606](https://github.com/eqrion/cbindgen/issues/606))
 * Allow controlling the cargo profile used for expansion. ([#607](https://github.com/eqrion/cbindgen/issues/607))
 * Support wider range of expressions in enum discriminants ([#614](https://github.com/eqrion/cbindgen/issues/614))
 * Support generation of Cython bindings ([#590](https://github.com/eqrion/cbindgen/issues/590))
 * Fixed some issues with style=tag and recursive structs ([#615](https://github.com/eqrion/cbindgen/issues/615))
 * Default C style to Both (as specified in docs) ([#615](https://github.com/eqrion/cbindgen/issues/615))
 * Fix resolution of path dependencies from certain modules. ([#629](https://github.com/eqrion/cbindgen/issues/629))
 * Support inlined definitions for tuple variants with a single field in C ([#631](https://github.com/eqrion/cbindgen/issues/631))

Thanks to all the awesome contributors that contributed to this release.

0.15.0

 * Allow customizing mangling of generic parameters in C ([#575](https://github.com/eqrion/cbindgen/issues/575))
 * Box<T> simplifies to T* in C (4ce324c)
 * ManuallyDrop<T> and MaybeUninit<T> simplify to T in C, and are opaque in C++ (0076a17)
 * C++ supports a derive-ostream annotation to derive serialization of structs, unions and enums ([#582](https://github.com/eqrion/cbindgen/issues/582))
 * Large character constants have been fixed on Windows ([#586](https://github.com/eqrion/cbindgen/issues/586))
 * Constants are now generated for typedefs, etc ([#589](https://github.com/eqrion/cbindgen/issues/589))
 * The `sort_by` configuration option has been made to work for constants ([#587](https://github.com/eqrion/cbindgen/issues/587))
 * Default sort order is source order now (sort_by = "None"), and can be changed by the above option ([#587](https://github.com/eqrion/cbindgen/issues/587))

... (truncated)

Commits

• 41506d5 v0.20.0
• 34299ae Don't use check profile when expanding code on a release build
• 6c96c8a Update --pretty=expanded to -Zunpretty=expanded
• 57add9c Fix some clippy lints.
• 63c1043 Simplify Pin<T> to T
• ccd1f0e add Builder::with_using_namespaces
• 4e39449 Ignore PhantomPinned
• 2d20c4b Move the target-guessing code from #676 to its own function.
• 93c06c5 Only fetch dependencies for current platform by default (#676)
• d9e490c v0.19.0
• Additional commits viewable in compare view

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