Update bindgen requirement from 0.66 to 0.68

[dependabot]

Updates the requirements on bindgen to permit the latest version.

Release notes

Sourced from bindgen's releases.

v0.68.1

Install bindgen-cli 0.68.1

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/rust-lang/rust-bindgen/releases/download/v0.68.1/bindgen-cli-installer.sh | sh

Install prebuilt binaries via powershell script

irm https://github.com/rust-lang/rust-bindgen/releases/download/v0.68.1/bindgen-cli-installer.ps1 | iex

Download bindgen-cli 0.68.1

File	Platform	Checksum
bindgen-cli-aarch64-apple-darwin.tar.xz	macOS Apple Silicon	checksum
bindgen-cli-x86_64-apple-darwin.tar.xz	macOS Intel	checksum
bindgen-cli-x86_64-unknown-linux-gnu.tar.xz	Linux x64	checksum

Changelog

Sourced from bindgen's changelog.

0.68.1

Fixed

• Fixed errors on the windows artifact build process.

0.68.0

Added

• The system ABI is now supported as an option for the --override-abi flag.
• The allowlist_item method and the --allowlist-item flag have been included to filter items regardless or their kind.
• Include installers as release artifacts on Github.

Changed

• The Clone implementation for _BindgenUnionField has been changed to pass the incorrect_clone_impl_on_copy_type Clippy lint.
• The c_unwind ABI can be used without a feature gate for any Rust target version equal to or greater than 1.71. This comes as a result of the ABI being stabilised (in Rust 1.71).
• Formatting changes when using prettyplease as a formatter due to a new prettyplease version.
• Avoid generating invalid CStr constants when using the --generate-cstr option.

Removed

• The extra_assert and extra_assert_eq macros are no longer exported.

Fixed

• Bindgen no longer panics when parsing an objective-C header that includes a Rust keyword that cannot be a raw identifier, such as: self, crate, super or Self.

0.67.0

This version was skipped due to some problems on the release workflow.

0.66.1

Removed

• Revert source order sorting (#2543) due to correctness regressions #2558.

0.66.0

Added

• Added the --generate-cstr CLI flag to generate string constants as &CStr instead of &[u8]. (Requires Rust 1.59 or higher.)
• Added the --generate-shell-completions CLI flag to generate completions for different shells.
• The --wrap-static-fns option can now wrap va_list functions as variadic functions with the experimental ParseCallbacks::wrap_as_variadic_fn method.
• Add target mappings for riscv32imc and riscv32imac.
• Add the ParseCallbacks::field_visibility method to modify field visibility.

... (truncated)

Commits

• 8d75a02 chore: Release
• a21e60b Release preparation for v0.68.1 (#2627)
• ebcf0bc chore: Release
• 59102e9 chore: Release
• f623bfb Don't release anything by default (#2623)
• 073fa62 test cli and lib msrv separately (#2625)
• b52377a Update CHANGELOG.md (#2622)
• 1d74af3 Don't delete the lockfile on the msrv workflow (#2621)
• ef2fb79 make search less surprising (#2613)
• ea3f8a7 there been editors not affilicated with Servo (#2615)
• Additional commits viewable in compare view

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