tor/changes/ticket27547

  o Major feature (hidden service v3):
    - Implement client authorization at the descriptor level. A new torrc
      option was added to control this client side: ClientOnionAuthDir <path>.
      On the service side, if the "authorized_clients/" directory exists in
      the onion service directory path, client configuration are read from the
      files within. See the manpage for more details. Closes ticket 27547.
      Patch done by Suphanat Chunhapanya (haxxpop).