Quite a backlog developed in the couple of weeks I was concentrating on tor
support. I've taken a first pass through it and fixed the most pressing
issues now. 

Most important was an ugly memory corruption problem in the GHC runtime
system that may have led to data corruption when using git-annex with Linux
kernels older than 4.5. All the Linux standalone builds of git-annex have
been updated to fix that issue.

Today dealt with several more things, including fixing a buggy timestamp
issue with `metadata --batch`, reverting the ssh ServerAliveInterval
setting (broke on too many systems with old ssh or complicated ssh
configurations), making batch input not be rejected when it can't be decoded
as UTF-8, and more.

Also, spent some time learning a little bit about Magic Wormhole and SPAKE,
as a way to exchange tor remote addresses. Using Magic Wormhole for that
seems like a reasonable plan. I did file a couple bugs on it which will
need to get fixed, and then using it is mostly a question of whether it's
easy enough to install that git-annex can rely on it.
