o Major features:
    - Relays now try regenerating and uploading their descriptor more
      frequently if they are not listed in the consensus, or if the
      version of their descriptor listed in the consensus is too
      old. This fix should prevent situations where a server declines
      to re-publish itself because it has done so too recently, even
      though the authorities decided not to list its recent-enough
      descriptor. Fix for bug 3327.

  o Minor features:
    - Relays now include a reason for regenerating their descriptors
      an HTTP header when uploading to the authorities.  This will
      make it easier to debug descriptor-upload issues in the future.