o Major bugfixes

    - Fix a rare assertion failure when checking whether a v0 hidden
      service descriptor has any usable introduction points left, and
      we don't have enough information to build a circuit to the first
      intro point named in the descriptor.  The HS client code in
      0.2.3.x no longer uses v0 HS descriptors, but this assertion can
      trigger on (and crash) v0 HS authorities.  Fixes bug 4411.
      Bugfix on 0.2.3.1-alpha; diagnosed by frosty_un.