Problem: commit afb24b53 broke ZMQ_STREAM contract

Symptom is that ZMQ_STREAM sockets in 4.1.0 and 4.1.1 generate zero
sized messages on each new connection, unlike 4.0.x which did not do
this.

Person who made this commit also changed test cases so that contract
breakage did not show. Same person was later banned for persistently
poor form in CZMQ contributions.

Solution: enable connect notifications on ZMQ_STREAM sockets using a
new ZMQ_STREAM_NOTIFY setting. By default, socket does not deliver
notifications, and behaves as in 4.0.x.

Fixes #1316

src/router.hpp

@@ -111,7 +111,7 @@ namespace zmq
         // If true, report EAGAIN to the caller instead of silently dropping 
         // the message targeting an unknown peer.
         bool mandatory;
-        bool raw_sock;
+        bool raw_socket;
 
         // if true, send an empty message to every connected router peer
         bool probe_router;