message: doc: Add IPv6 address to zmq example
diff: @@ -84,7 +84,7 @@ For instance:
  $ peercoind -zmqpubhashtx=tcp://127.0.0.1:28332 \
  -zmqpubhashtx=tcp://192.168.1.2:28332 \
  - -zmqpubrawtx=ipc:///tmp/peercoind.tx.raw \
  + -zmqpubhashblock="tcp://[::1]:28333" \
  -zmqpubhashtxhwm=10000
  Each PUB notification has a topic and body, where the header
  @@ -125,6 +125,9 @@ Setting the keepalive values appropriately for your operating environment may
  improve connectivity in situations where long-lived connections are silently
  dropped by network middle boxes.
  +Also, the socket's ZMQ_IPV6 option is enabled to accept connections from IPv6
  +hosts as well. If needed, this option has to be set on the client side too.
  +
  ## Remarks
  From the perspective of peercoind, the ZeroMQ socket is write-only; PUB
  