o Major bugfixes:
   - Fix a stupid parenthesization error that made every possible value
     of CircPriorityHalflifeMsec get treated as "1 msec".  Bugfix on
     0.2.2.7-alpha.
   - Rename CircPriorityHalflifeMsec to CircuitPriorityHalflifeMsec,
     so authorities can tell newer relays about the option without
     breaking older ones.