Update cbindgen requirement from 0.14 to 0.15

[dependabot-preview]

Updates the requirements on cbindgen to permit the latest version.

Changelog

Sourced from cbindgen's changelog.

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))

0.14.6

 * Fixed the builds with older versions of rustc.

0.14.5

 * Add support to specify line ending style ([#568](https://github.com/eqrion/cbindgen/issues/568))
 * Add cbindgen:ptrs-as-arrays annotation to allow making function
   arguments C/C++ arrays.

0.14.4

 * Allow to override the mangling separator ([#502](https://github.com/eqrion/cbindgen/issues/502))


cbindgen now handles better having ZSTs in template parameters, and
default template parameters (#563).


Support for annotating nonnull pointers (#558)


Fixed bitflags that overflow a signed integer (#556)


Support for wildcard argument names (#550)


Support for the never return type, with configurable annotation (#549)


Properly reject arrays as function arguments (#540)

0.14.3

 * Introduce cbindgen:ignore comment annotation, to allow ignoring items or modules. ([#519](https://github.com/eqrion/cbindgen/issues/519))
 * Support for casts in constant expressions. ([#526](https://github.com/eqrion/cbindgen/issues/526))
 * Make a non-fatal error a warning message. ([#535](https://github.com/eqrion/cbindgen/issues/535))
 * Add a --metadata option to the CLI, to allow passing pre-computed cargo metadata. ([#538](https://github.com/eqrion/cbindgen/issues/538))

0.14.2

 * Fixed minimal dependency versions. ([#507](https://github.com/eqrion/cbindgen/issues/507))
 * Add an option to write pragma once. ([#511](https://github.com/eqrion/cbindgen/issues/511))
 * Fix submodule scanning for implicit Rust 2018 modules. ([#512](https://github.com/eqrion/cbindgen/issues/512))

Commits

• 83b3be9 v0.15.0
• aeb69bc Switch default sorting order for items to "None"
• ea919a4 mem::replace -> mem::take
• f3d5a20 Support sort_by for constants
• 6439e6d Support constants with arbitrary types
• 9669cad Rename ARCHITECTURE.md to internals.md in contributing instructions
• 56d0799 Use U'...' character literals instead of L'...' character literals
• f4b26fe Checkout files with LF line endings
• d1d97d4 enumeration: Only propagate derive_ostream annotation if not present.
• 36a3f8b enumertion: Add a using declaration rather than qualifying all branches.
• Additional commits viewable in compare view

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[Ortham]

@dependabot rebase