Add name_lookup function in object_ops.

diff --git a/server/signal.c b/server/signal.c
index 2888015..d90739f 100644
--- a/server/signal.c
+++ b/server/signal.c
@@ -64,6 +64,7 @@
     NULL,                     /* satisfied */
     no_signal,                /* signal */
     no_get_fd,                /* get_fd */
+    no_lookup_name,           /* lookup_name */
     no_close_handle,          /* close_handle */
     handler_destroy           /* destroy */
 };