MEDIUM: protocol: add a pointer to struct sock_ops to the listener struct

The listener struct is now aware of the socket layer to use upon accept().
At the moment, only sock_raw is supported so this patch should not change
anything.
diff --git a/include/types/protocols.h b/include/types/protocols.h
index bda4922..ac52a53 100644
--- a/include/types/protocols.h
+++ b/include/types/protocols.h
@@ -102,6 +102,7 @@
 	int options;			/* socket options : LI_O_* */
 	struct licounters *counters;	/* statistics counters */
 	struct protocol *proto;		/* protocol this listener belongs to */
+	struct sock_ops *sock;          /* listener socket operations */
 	int nbconn;			/* current number of connections on this listener */
 	int maxconn;			/* maximum connections allowed on this listener */
 	unsigned int backlog;		/* if set, listen backlog */