Migrate from winapi to windows-sys

[jessebraham]

The winapi crate is no longer maintained, and Microsoft are now maintaining the windows-sys crate (among others), so we should migrate to this.

[DoumanAsh]

I would recommend not to hurry with it because windows-sys makes semver incompatible bumps with each new version so it would become annoying and eventually stale in this crate

[caspermeijn]

Today I tried this conversion, but it is currently not straightforward.

The DCB struct has a lot of bitfields, which are much used in serialport. The bitfields don't have easy getters/setters yet: microsoft/windows-rs#2942 Therefore doing the conversion today would decrease the code readability.

[sirhcel]

Thank you for attempting the migration @caspermeijn! Do you have some work-in-progress to share with us (at best in a fork) so that I can have a look at how exactly this gets messy?

[caspermeijn]

Thank you for attempting the migration @caspermeijn! Do you have some work-in-progress to share with us (at best in a fork) so that I can have a look at how exactly this gets messy?

This was my work in progress commit: caspermeijn@58ab9ba

I didn't work on the bit fields when I saw the mentioned lack of support. The problem comes down to this:
DCB::_bitfield is an integer field, but it represents multiple bit fields. The windows-rs crate doesn't provide any help, so serialport needs to maintain a list of the bit indexes. That sounded like not the core competency of this crate and should be provided by a Windows API crate instead. The maintainer of windows-rs seems to be aware of that.