Fix the version check with msysgit

With v1.9.0, msysgit put the packaging info like  1.9.0.msysgit.0, instead
of 1.9.0.0.msysgit.0, like I expected.  Now, we'll make it work, even if
they do something like 2.msysgit.0 or 2.0.msysgit.234.asdf.