Rust 101 - 27: Exercises for module C (q2)

Implementing a simplified form of `Mutex`. Links: * Exercises: https://artificialworlds.net/presentations/rust-101/exercises/C-concurrency-parallelism/mod.html * Slides: https://artificialworlds.net/presentations/rust-101/C-concurrency-parallelism Rust 101 is a series of videos explaining how to write programs in Rust. The course materials for this series are developed by tweede golf. You can find more information at https://github.com/tweedegolf/101-rs and you can sponsor the work at https://github.com/sponsors/tweedegolf . They are released under the Creative Commons Attribution Share Alike 4.0 International license. This series of videos is copyright 2024 Andy Balaam and the tweede golf contributors and is released under the [Creative Commons Attribution Share Alike 4.0 International license](https://creativecommons.org/licenses/by-sa/4.0/).