Update Bindgen for Compatibility with macOS 11

The version of Rust Bindgen prior to 0.56 would not compile on macOS 11.
Bumping the dependency version of Bindgen to fix this bug in
CoreAudio-Sys.

Author: ootoovak

Cargo.toml

@@ -11,7 +11,7 @@ repository = "https://github.com/RustAudio/coreaudio-sys.git"
 build = "build.rs"
 
 [build-dependencies.bindgen]
-version = "0.53"
+version = "0.56"
 default-features = false
 features = ["runtime"]