Preparing for a release (probably tomorrow or Friday).

Part of that was updating the autobuilders. Had to deal with the gnutls
security hole fix, and upgrading that on the OSX autobuilder turned out to
be quite complicated due to library version skew. Also, I switched the
linux autobuilders over to building from Debian unstable, rather than
stable. That should be ok to do now that the standalone build bundles all
the libraries it needs... And the arm build has always used unstable, and
has been reported working on a lot of systems. So I think this will be
safe, but have backed up the old autobuilder chroots just in case.

Also been catching up on bug reports and traffic and 
and dealt with quite a lot of things today. Smarter log file
rotation for the assistant, better webapp behavior when git is not
installed, and a fix for the webdav 5 second timeout problem.

Perhaps the most interesting change is a new `annex.startupscan` setting,
which can be disabled to prevent the assistant from doing the expensive
startup scan. This means it misses noticing any files that changed since it
last run, but this should be useful for those really big repositories.

(Last night, did more work on the test suite, including even more checking
of merge conflict resolution.)

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Today's work was sponsored by Michael Alan Dorman.
