More improvements to tor support. Yesterday, debugged a reversion that
broke push/pull over tor, and made actual useful error messages be
displayed when there were problems. Also fixed a memory leak, although I
fixed it by reorganizing code and could not figure out quite why it happened,
other than that the ghc runtime was not managing to be as lazy as I would
expect. 

Today, added git ref change notification to the
P2P protocol, and made the remotedaemon automatically fetch changes from
tor remotes. So, it should work to use the assistant to keep
repositories in sync over tor. I have not tried it yet, and linking over tor
still needs to be done at the command line, so it's not really ready for
webapp users yet.

Also fixed a denial of service attack in git-annex-shell and git-annex when
talking to a remote git-annex-shell. It was possible to feed either a large
amount of data when they tried to read a line of data, and summon the OOM
killer. Next release will be expedited some because of that.

Today's work was sponsored by Thomas Hochstein on Patreon.
