[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/ackvec.h b/net/dccp/ackvec.h
index 2424eff..cf8f20c 100644
--- a/net/dccp/ackvec.h
+++ b/net/dccp/ackvec.h
@@ -28,8 +28,7 @@
 
 /** struct dccp_ackvec - ack vector
  *
- * This data structure is the one defined in the DCCP draft
- * Appendix A.
+ * This data structure is the one defined in RFC 4340, Appendix A.
  *
  * @dccpav_buf_head - circular buffer head
  * @dccpav_buf_tail - circular buffer tail