Replace winapi with windows-sys?

[Jake-Shadle]

I was updating mio to use windows-sys instead of winapi as windows-sys covers most of Windows API surface and most importantly is maintained and updated frequently as opposed to winapi, but this crate still provides types and functions not available in the windows-sys crate which is to be expected, however since it relies on winapi internally we'll be pulling in 2 versions of windows bindings, and in some cases need to transmute between the "same" type, so just wanted to open this issue to begin a discussion about whether this is something that would be acceptable to this project.

[ghost]

I agree on this one, winapi can already be seen as deprecated, since there is the official windows crate.

https://github.com/microsoft/windows-rs
https://crates.io/crates/windows-sys