No windows support for git-remote-osf

[mih]

I have no idea why it isn't working, but it is not. The starting point for forensics is #106 (comment)

I would very much appreciate if a person familiar with Git on Windows could have a look.

[mih]

With #176 this code is replace with an implementation that is known to work on windows. Moreover the special remote test battery now also runs on windows.