MINOR: stream-int: add a new flag to mention that we want the connection to be killed

The new flag SI_FL_KILL_CONN is now set by the rare actions which
deliberately want the whole connection (and not just the stream) to be
killed. This is only used for "tcp-request content reject",
"tcp-response content reject", "tcp-response content close" and
"http-request reject". The purpose is to desambiguate the close from
a regular shutdown. This will be used by the next patches.
diff --git a/include/proto/stream_interface.h b/include/proto/stream_interface.h
index 5800c1e..3cccc8f 100644
--- a/include/proto/stream_interface.h
+++ b/include/proto/stream_interface.h
@@ -420,6 +420,12 @@
 	si->ops->shutw(si);
 }
 
+/* Marks on the stream-interface that next shutw must kill the whole connection */
+static inline void si_must_kill_conn(struct stream_interface *si)
+{
+	si->flags |= SI_FL_KILL_CONN;
+}
+
 /* This is to be used after making some room available in a channel. It will
  * return without doing anything if the stream interface's RX path is blocked.
  * It will automatically mark the stream interface as busy processing the end