Cygwin has a recent Git now.

Also make the `grep` we run to determine our version of Git quiet. (We
want to know if our version string matches, but there's no need to print
it to the console.)
Enable autocrlf for Windows.

I don't think this will cause any headaches when I'm working on OS X
or Linux, so I'm going to set it and I'll find a way to do it only on
Windows if I have any issues.