[MERGE][#109143] Support bzr+ssh://host/~/path

[Martin Pool]

For the sake of the list, I spoke about Andrew to this today and he
said he'd come around to thinking it should be done by sending ~ in
the protocol rather than at the ssh layer.  He might look at it again
after working on the stacking bugs.  Doing it this way does have the
slight disadvantage that it will only work when the server is new
enough to support it.  (Though maybe it will have the corresponding
advantage that it will work even with old clients.)

-- 
Martin <http://launchpad.net/~mbp/>