New windows version query in configure

[gaborcsardi]

Because the old one fails on non-English systems.

The code is now in an R file, so that we can test it better.

It tries to use wmic first. wmic should produce the same output,
irrespectively of the language. It wmic fails, e.g. because it is
not available, then we fall back to ver, but use a much more forgiving
regex. As long as the version number is the last word within square
brackets, this should work.

Closes #69