MINOR: tcp: add custom actions that can continue tcp-(request|response) processing

Actually, the tcp-request and tcp-response custom ation are always final
actions. This patch create a new type of action that can permit to
continue the evaluation of tcp-request and tcp-response processing.
diff --git a/include/types/proto_tcp.h b/include/types/proto_tcp.h
index ce21dae..f41933b 100644
--- a/include/types/proto_tcp.h
+++ b/include/types/proto_tcp.h
@@ -40,6 +40,7 @@
 	TCP_ACT_CLOSE, /* close at the sender's */
 	TCP_ACT_CAPTURE, /* capture a fetched sample */
 	TCP_ACT_CUSTOM, /* Use for custom registered keywords. */
+	TCP_ACT_CUSTOM_CONT, /* Use for custom registered keywords. */
 };
 
 struct capture_prm {