FreeBSD doesn't define MSG_ERRQUEUE -- now it's defined in 0MQ

src/pgm_socket.cpp

@@ -40,6 +40,10 @@
 #include "uuid.hpp"
 #include "stdint.hpp"
 
+#ifndef MSG_ERRQUEUE
+#	define MSG_ERRQUEUE		0x2000
+#endif
+
 zmq::pgm_socket_t::pgm_socket_t (bool receiver_, const options_t &options_) :
     sock (NULL),
     options (options_),