o Minor bugfixes (logging):
    - Downgrade logs and backtraces about IP versions to
      info-level. Only log backtraces once each time tor runs.
      Assists in diagnosing bug 18351; bugfix on c3cc8e16e in
      tor-0.2.8.1-alpha.
      Reported by "sysrqb" and "Christian", patch by "teor".