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 INTRODUCE2 cells 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.