Problem: no documentation on zmq_socket_monitor_versioned

Solution: add initial version of documentation

doc/zmq_socket_monitor.txt

@@ -21,6 +21,11 @@ method creates a 'ZMQ_PAIR' socket and binds that to the specified
 inproc:// 'endpoint'. To collect the socket events, you must create
 your own 'ZMQ_PAIR' socket, and connect that to the endpoint.
 
+Note that there is also a DRAFT function linkzmq:zmq_socket_monitor_versioned[3],
+which allows to subscribe to events that provide more information.
+Calling zmq_socket_monitor is equivalent to calling 'zmq_socket_monitor_versioned'
+with the 'event_version' parameter set to 1, with the exception of error cases.
+
 The 'events' argument is a bitmask of the socket events you wish to
 monitor, see 'Supported events' below. To monitor all events, use the
 event value ZMQ_EVENT_ALL. NOTE: as new events are added, the catch-all
@@ -31,7 +36,7 @@ guarantee compatibility with future versions.
 Each event is sent as two frames. The first frame contains an event
 number (16 bits), and an event value (32 bits) that provides additional
 data according to the event number. The second frame contains a string
-that specifies the affected TCP or IPC endpoint.
+that specifies the affected endpoint.
 
 ----
 The _zmq_socket_monitor()_ method supports only connection-oriented