Running clippy.

[pauldotknopf]

Should we add these checks to the build server?

[Enet4]

These look good, thank you!

Adding Clippy to CI could be done, but not without extra care, since not all toolchains may have it successfully built and available. As a noteworthy example, the Rustup clippy tool hasn't been available since nightly-2019-09-14 (see Rustup components history). We can include it, but a successful installation should not be mandatory.