Add a disconnect method (interface to the zmq_disconnect call) in the socket_t class

zmq.hpp

@@ -358,6 +358,13 @@ namespace zmq
                 throw error_t ();
         }
 
+        inline void disconnect (const char *addr_)
+        {
+            int rc = zmq_disconnect (ptr, addr_);
+            if (rc != 0)
+                throw error_t ();
+        }
+
         inline bool connected()
         {
             return(ptr != NULL);