o Minor bugfixes:
    - Exit nodes didn't recognize EHOSTUNREACH as a plausible error
      code, and sent back END_STREAM_REASON_MISC.  They now send a a
      new stream ending reason: END_STREAM_REASON_NOROUTE. Also update
      the spec to reflect this new reason. Bugfix on 0.1.0.1-rc; fixes
      bug 1793.