0MQ version 4.2.5 stable, released on 2018/03/23

• Fixed #3018 - fix backward-incompatible change in the NULL auth
  mechanism that slipped in 4.2.3 and made connections
  with a ZAP domain set on a socket but without a working
  ZAP handler fail. See ZMQ_ZAP_ENFORCE_DOMAIN and RFC27.

• Fixed #3016 - clarify in zmq_close manpage that the operation will
  complete asynchronously.

• Fixed #3012 - fix CMake build problem when using LIBZMQ_WERROR and a
  compiler other than GCC.