msvc builds on the buildfarm

Thanks to Dave, we now have a couple of machines on the buildfarm that build with msvc - a definite requirement for using the msvc build for the main binary distribution of 8.3. Today had my first msvc-specific patch that the buildfarm found for us - a trivial overlook, but the buildfarm certainly helped. And even the Unix folks seem to like it - diversity is good for portability.