tor/changes/no_client_timestamps_024

  o Minor features (security, timestamp avoidance, proposal 222):
    - Clients no longer send timestamps in their NETINFO cells.  These were
      not used for anything, and they provided one small way for clients
      to be distinguished from each other as they moved from network to
      network or behind NAT. Implements part of proposal 222.
    - Clients now round timestamps in INTRODUCE cells down to the nearest
      10 minutes.  If a new Support022HiddenServices option is set to 0,
      or if it's set to "auto" and the feature is disabled in the consensus,
      the timestamp is sent as 0 instead. Implements part of proposal 222.
    - Stop sending timestamps in AUTHENTICATE cells. This is not such
      a big deal from a security point of view, but it achieves no actual
      good purpose, and isn't needed. Implements part of proposal 222.
    - Reduce down accuracy of timestamps in hidden service descriptors.
      Implements part of proposal 222.