minor problem in zmq_poll (select version) fixed

src/zmq.cpp

@@ -539,7 +539,7 @@ int zmq_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
             memcpy (&inset, &pollset_in, sizeof (fd_set));
             memcpy (&outset, &pollset_out, sizeof (fd_set));
             memcpy (&errset, &pollset_err, sizeof (fd_set));
-            int rc = select (maxfd, &inset, &outset, &errset,
+            int rc = select (maxfd + 1, &inset, &outset, &errset,
                 first_pass ? &zero_timeout : (timeout_ < 0 ? NULL : &timeout));
 #if defined ZMQ_HAVE_WINDOWS
             wsa_assert (rc != SOCKET_ERROR);