Cleanup Apple implementation

[complexspaces]

This PR resolves the confusing type size implications pointed out in a recent report and additionally cleans up the other type casing done inside the Apple implementation to be cleaner. It also handles a trivial libc deprecation I noticed opening up a fresh clone of the repository.

Commit-by-commit review is recommended.

Closes #22

[complexspaces]

Interestingly, the tests sometimes fail on my MacBook, both on main and this branch:

thread 'main' (10399431) panicked at tests.rs:41:9:
assertion `left == right` failed
  left: Some(false)
 right: Some(true)
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I'm not sure if this is just a fluke or something to be worried about.

[jhpratt]

That's definitely unexpected. Returning false is always an acceptable answer given the soundness implications. I don't know enough about MacOS to know if there is always another process underneath.

To be totally honest, I don't really need this crate any more, as the only time it's used in the time crate is in a method that is rarely if ever called. So this is not exactly a high priority for me. I very much appreciate you helping out, though! OS-level things aren't my forte.