zebra: freshen RFC references in rtadv

RFC2461 was replaced by RFC4861
RFC3775 was replaced by RFC6275
draft-ietf-mip6-mipext-advapi-03 was replaced by RFC4584
diff --git a/zebra/rtadv.h b/zebra/rtadv.h
index 5bf6b84..564a4c6 100644
--- a/zebra/rtadv.h
+++ b/zebra/rtadv.h
@@ -47,7 +47,7 @@
   /* The value to be placed in the Autonomous Flag. */
   int AdvAutonomousFlag;
 
-  /* The value to be placed in the Router Address Flag (RFC3775 7.2). */
+  /* The value to be placed in the Router Address Flag [RFC6275 7.2]. */
   int AdvRouterAddressFlag;
 #ifndef ND_OPT_PI_FLAG_RADDR
 #define ND_OPT_PI_FLAG_RADDR         0x20
@@ -58,7 +58,7 @@
 extern void rtadv_config_write (struct vty *, struct interface *);
 extern void rtadv_init (void);
 
-/* draft-ietf-mip6-mipext-advapi-03 */
+/* RFC4584 Extension to Sockets API for Mobile IPv6 */
 
 #ifndef ND_OPT_ADV_INTERVAL
 #define ND_OPT_ADV_INTERVAL	7   /* Adv Interval Option */