Add support for Windows

[jodersky]

This is a community issue, anyone is welcome to pick it up.

Flow's native libary is written in C and aims to be portable by only using the standard POSIX API. However, since Windows does not provide support for the API, flow currently cannot be compiled for it.
Resolving this issue would require an additional native implementation, similar to the current posix one.

A potential starting point is provided here. Essentially, all that is required is an implementation of flow.h.

Please feel free to comment here or ask on the chat. Any help on providing Windows support out-of-the-box is greatly appreciated!

[jodersky]

To whom it may concern, I haven't checked it but, could the new Windows 10 Subsystem for Linux help in supporting flow?

[cessationoftime]

I have put some work into this here: https://github.com/cessationoftime/akka-serial
But I am not sure yet if I will get around to completing it.