[RFC] Support new authentication exchange format

[Kevin Cernekee]

On Tue, Feb 5, 2013 at 1:55 PM, David Woodhouse <dwmw2 at infradead.org> wrote:
> Hm, it's *really* time we cut a new release. Could you look over the
> patches I've committed in the last day or so, which reinstate
> compatibility with my simple test server? If you don't see any problem,
> I'll call it 4.99...

I retested the head of tree and reviewed the code changes; everything looks OK.