Update windows ffi bindings Bump `windows-bindgen` to version 0.51.1. This brings with it some changes to the generated FFI bindings, but little that affects the code. One change that does have more of an impact is `SOCKET` being `usize` instead of either `u64` or `u32` (as is used in std's public `SOCKET` type). However, it's now easy enough to abstract over that difference. Finally I added a few new bindings that are likely to be used in pending PRs, mostly to make sure they're ok with the new metadata. r? libs