ospf6d: Have ospf6d cleanup when it terminates normally

A clean exit makes it easier to use memory debuggers.

* ospf6_asbr.c: (ospf6_asbr_terminate) Add a function to do route map
  cleanup.
* ospf6_lsa.c: (ospf6_lsa_terminate) Add a function to cleanup the lsa
  handler vector.
* ospf6_main.c: (ospf6_exit) Add an function that causes ospf6d to
  gracefully exit.
* ospf6_message.c: (ospf6_message_terminate) Add a function that frees
  the send and receive buffers.
* ospf6_top.c: (ospf6_delete) Enable the ospf6_delete() function.
  Disable ospf6 before freeing everything.
diff --git a/ospf6d/ospf6_lsa.c b/ospf6d/ospf6_lsa.c
index c1db374..588b946 100644
--- a/ospf6d/ospf6_lsa.c
+++ b/ospf6d/ospf6_lsa.c
@@ -712,6 +712,11 @@
   ospf6_install_lsa_handler (&unknown_handler);
 }
 
+void
+ospf6_lsa_terminate (void)
+{
+  vector_free (ospf6_lsa_handler_vector);
+}
 
 static char *
 ospf6_lsa_handler_name (struct ospf6_lsa_handler *h)