tor/changes/deprecation

  o Major features (user interface):
    - Tor now supports the ability to declare options deprecated, so that
      we can recommend that people stop using them. Previously, this was
      done in an ad-hoc way.
      Closes ticket 19820.

  o Minor features (user interface):
    - There is a new --list-deprecated-options command-line option to list
      all of the deprecated options. Implemented as part of ticket 19820.

  o Deprecated features:
    - A number of options are deprecated for security reasons, and may be
      removed in a future version of Tor. The options are: AllowDotExit,
      AllowInvalidNodes, AllowSingleHopCircuits, AllowSingleHopExits,
      ClientDNSRejectInternalAddresses,
      CloseHSClientCircuitsImmediatelyOnTimeout,
      CloseHSServiceRendCircuitsImmediatelyOnTimeout, ExcludeSingleHopRelays,
      FastFirstHopPK, TLSECGroup, UseNTorHandshake, and WarnUnsafeSocks.

    - A number of DNS-cache-related sub-options for client ports are now
      deprecated for security reasons, and may be removed in a future version
      of Tor. (We believe that client-side DNS cacheing is a bad idea for
      anonymity, and you should not turn it on.) The options are: CacheDNS,
      CacheIPv4DNS, CacheIPv6DNS, UseDNSCache, UseIPv4Cache, and
      UseIPv6Cache.

    - The *ListenAddress options are now deprecated as unnecessary: the
      corresponding *Port options should be used instead. These options may
      someday be removed.  The affected options are: ControlListenAddress,
      DNSListenAddress, DirListenAddress, NATDListenAddress, ORListenAddress,
      SocksListenAddress, and TransListenAddress.