Module fd

Export the *Fd types and traits that are used in rustix's public API.

This module exports the types and traits from std::os::fd, or polyills on Rust < 1.66 or on Windows.

On Windows, the polyfill consists of aliases of the socket types and traits, For example, OwnedSocket is aliased to OwnedFd, and so on, and there are blanket impls for AsFd etc. that map to AsSocket impls. These blanket impls suffice for using the traits, however not for implementing them, so this module also exports AsSocket and the other traits as-is so that users can implement them if needed.