[NET]: Introduce inet_connection_sock

This creates struct inet_connection_sock, moving members out of struct
tcp_sock that are shareable with other INET connection oriented
protocols, such as DCCP, that in my private tree already uses most of
these members.

The functions that operate on these members were renamed, using a
inet_csk_ prefix while not being moved yet to a new file, so as to
ease the review of these changes.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 334717b..b7c7eec 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -224,17 +224,17 @@
 	return prev_qlen;
 }
 
-static inline int reqsk_queue_len(struct request_sock_queue *queue)
+static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 {
 	return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
 }
 
-static inline int reqsk_queue_len_young(struct request_sock_queue *queue)
+static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 {
 	return queue->listen_opt->qlen_young;
 }
 
-static inline int reqsk_queue_is_full(struct request_sock_queue *queue)
+static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
 {
 	return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
 }