Add Appveyor support

[ndmitchell]

Requested by @hvr.

[hvr]

Do I need to do anything to make this work? :-)

[ndmitchell]

You can see the results at https://ci.appveyor.com/project/ndmitchell/win32. You should sign up for an appveyor account and then add it (very easy), and it will build automatically.

Note this is my standard Stack appveyor setup. I tend to do aggressive checks on Travis (no \r newlines, no missing files in the Cabal list, no warnings etc), and then leave appveyor to just check it builds/passes tests. Given this project, you may want to insert some -Werror into it somewhere.

[hvr]

Well, problem is, we can't use Travis at all, because Win32 is a windows-only package... :-)

[ndmitchell]

Merge. Get an Appveyor account. Log into Appveyor. Projects. Add Project. Win32 (+). That's about it, very smooth.

Yep, I appreciate my standard approach will fail here, so you might need to push more into Appveyor, while I keep it deliberately light.

[hvr]

one last question: say I wanted to enable -Werror or some other ghc warning flags for the validation... how would I do that?

[ndmitchell]

Change the stack build line to include things like --ghc-options -Werror, I think, but I'm not an expert there.