tcp: Remove TCPCT

TCPCT uses option-number 253, reserved for experimental use and should
not be used in production environments.
Further, TCPCT does not fully implement RFC 6013.

As a nice side-effect, removing TCPCT increases TCP's performance for
very short flows:

Doing an apache-benchmark with -c 100 -n 100000, sending HTTP-requests
for files of 1KB size.

before this patch:
	average (among 7 runs) of 20845.5 Requests/Second
after:
	average (among 7 runs) of 21403.6 Requests/Second

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 4f9f5eb..ebc54fe 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -500,8 +500,7 @@
 	return &rt->dst;
 }
 
-static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
-				 struct request_values *rv_unused)
+static int dccp_v4_send_response(struct sock *sk, struct request_sock *req)
 {
 	int err = -1;
 	struct sk_buff *skb;
@@ -658,7 +657,7 @@
 	dreq->dreq_gss     = dreq->dreq_iss;
 	dreq->dreq_service = service;
 
-	if (dccp_v4_send_response(sk, req, NULL))
+	if (dccp_v4_send_response(sk, req))
 		goto drop_and_free;
 
 	inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);