Add reference to the inproc documentation

The previous note in connect introduced but did not elaborate on the
requirement to bind before connect in inproc. As that discussion is in
detail in the inproc docs link to there.

doc/zmq_connect.txt

@@ -42,7 +42,8 @@ Thus a successful invocation of _zmq_connect()_ does not indicate that a
 physical connection was or can actually be established. Because of this, for most 
 socket types the order in which a listening socket is bound and a connecting socket 
 is connected does not matter. However, for inproc:// scheme sockets, the zmq_bind() 
-must be executed before any sockets zmq_connect() to that endpoint
+must be executed before any sockets zmq_connect() to that endpoint. Refer to 
+linkzmq:zmq_inproc[7] for more details.
 
 
 RETURN VALUE