o Major bugfixes:
    - Reject bogus create and relay cells with 0 circuit ID or 0 stream
      ID: these could be used to create unexpected streams and circuits
      which would count as "present" to some parts of Tor but "absent"
      to others, leading to zombie circuits and streams or to a
      bandwidth DOS. Fixes bug 7889; bugfix on every released version of
      Tor. Reported by "oftc_must_be_destroyed".