[DCCP]: Update documentation references.

Updates the references to spec documents throughout the code, taking into
account that

* the DCCP, CCID 2, and CCID 3 drafts all became RFCs in March this year

* RFC 1063 was obsoleted by RFC 1191

* draft-ietf-tcpimpl-pmtud-0x.txt was published as an Informational
  RFC, RFC 2923 on 2000-09-22.

All references verified.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/options.c b/net/dccp/options.c
index 07a3469..fb0db1f 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -215,7 +215,7 @@
 				      elapsed_time);
 			break;
 			/*
-			 * From draft-ietf-dccp-spec-11.txt:
+			 * From RFC 4340, sec. 10.3:
 			 *
 			 *	Option numbers 128 through 191 are for
 			 *	options sent from the HC-Sender to the