Valery Vybornov

Basic Rust 2021 compatibility. In particular, this PR fixes the following error that appear under rust-analyzer: ``` error[E0308]: mismatched types --> /workspaces/src/mmal-sys/src/lib.rs:290:35 | 290 | ::std::str::from_utf8(&self.camera_name).unwrap(), | --------------------- ^^^^^^^^^^^^^^^^^ expected...