[IronPython] The elephant in the room: source control for IronPython

[Adal Chiriliuc]

I would prefer Mercurial for the simple reason that git is not very
well supported on Windows and it's ports are not robust enough.

And I would dump pre 2.7 history if it's too much of a hassle to
convert. If someone would really need to check ancient history, it
could just use the old repository.

I would also strive to have a smallish repository. I once tried to
check out the WebKit code and gave up after 4 hours of downloading and
hundred of thousands of files created on my disk.