Merge pull request #3049 from maksqwe/fix_fd_cast

Fix fd_t variable casting on Windows platform

src/tcp_listener.cpp

@@ -131,7 +131,7 @@ void zmq::tcp_listener_t::in_event ()
     session->inc_seqnum ();
     launch_child (session);
     send_attach (session, engine, false);
-    socket->event_accepted (endpoint, (int) fd);
+    socket->event_accepted (endpoint, fd);
 }
 
 void zmq::tcp_listener_t::close ()