Merge pull request #437 from rohanbedarkar/master

Explicit comments

src/pgm_socket.cpp

@@ -326,6 +326,7 @@ int zmq::pgm_socket_t::init (bool udp_encapsulation_, const char *network_)
 
     //  Set IP level parameters.
     {
+		// Multicast loopback disabled by default
 		const int multicast_loop = 0;
 		if (!pgm_setsockopt (sock, IPPROTO_PGM, PGM_MULTICAST_LOOP,
 		      &multicast_loop, sizeof (multicast_loop)))