Update bindgen requirement from 0.55 to 0.56

Updates the requirements on [bindgen](https://github.com/rust-lang/rust-bindgen) to permit the latest version.
- [Release notes](https://github.com/rust-lang/rust-bindgen/releases)
- [Changelog](https://github.com/rust-lang/rust-bindgen/blob/master/CHANGELOG.md)
- [Commits](rust-lang/rust-bindgen@v0.55.0...v0.56.0)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Cargo.toml

@@ -14,5 +14,5 @@ license = "LGPL-3.0"
 [dependencies]
 
 [build-dependencies]
-bindgen = "0.55"
+bindgen = "0.56"
 cmake = "0.1"