fix: windows build

[jerzyjamroz]

• add windows-x64-mingw cross-compilation
• add windows build
• remove '.appveyor.yml'

[anjohnson]

GHA does have Windows runners that you could test on too (see the epics-base job configuration for how), and they don't fail randomly in the same way that Appveyor jobs do. I'm not saying you need to add them though, I don't know if devLib2 is used on Windows at all, I didn't write this code.

The cross-build addition is probably a good thing to do, if only to prove that some Linux-specific code isn't hiding inside.

[mdavidsaver]

I don't know if devLib2 is used on Windows at all

It was at some point. At PSI as I recall. Which is why Dirk did #11. The matching Windows kernel driver source was (I think) never published, and would in any even need to be signed by M$ to use.

@dirk-zimoch Do you know if there is still any use of devlib2 on Windows at PSI?

[jerzyjamroz]

@mdavidsaver , it works fine for windows-latest. If all ok, I will merge it next week.