Migrating from winapi to windows-sys

[vthib]

windows-sys (and windows) are crates for bindings on Windows API officially supported by Microsoft. They are replacing winapi in many crates, and it would be nice to migrate this great project too :)

The differences in the API call are minimal. The other differences are mainly in the type used for constants, which can vary between i32 and u32, and is often not the same as the winapi one.

[pronebird]

Would be cool to see this merged.