[libvirt] More CI options

Since the addition of Travis CI builds, there is some more progress towards more testing. I was just wondering if anyone was thinking about (or is already working on) some settings for other CI environments as well. For example if configured AppVeyor, we could have MSVC builds as well. And there are more of those, I didn't compare all of them, but the more environments we have, the more build failures we might catch. Or even test failures, maybe. Martin