Removing unsafe by replacing libc with nix

[polachok]

Removing unsafe by replacing libc with nix

[polachok]

Hi,

I'm happy the project was useful for you!

Now to the point, I actually considered using nix, but decided against it for two reasons:

1.minimal dependencies
I think, in a teaching project, it makes sense to minimize dependencies, as every dependency adds cognitive load. A reader may be unfamiliar with nix, so they would have to consult nix docs. On the other hand, libc::select makes it clear that this is a well known C select function.

2.nix being huge
Nix covers a lot of APIs and consists of ~20k lines + 4 dependencies. Well, even mio dropped nix because it's heavy.

So, considering this, what do you think about adding a safe wrapper around select to fahrenheit itself? It would look as safe as nix in the main file, but a curious reader could inspect it in some util.rs right here.