  o Major bugfixes (circuit prediction):
    - Fix circuit prediction logic so that a client doesn't treat a stream as
      being "handled" by a circuit if that circuit already has isolation
      settings on it that might make it incompatible with the stream. This
      change should make Tor clients more responsive by improving their
      chances of having a pre-created circuit ready for use when a new client
      request arrives.  Fixes bug 18859; bugfix on 0.2.3.3-alpha.
