MINOR: stream_interface: add a client target : TARG_TYPE_CLIENT

This one will be used to identify the direction the SI is being used. All
incoming connections have a target of type TARG_TYPE_CLIENT.
diff --git a/include/proto/stream_interface.h b/include/proto/stream_interface.h
index 2123696..cbe8282 100644
--- a/include/proto/stream_interface.h
+++ b/include/proto/stream_interface.h
@@ -56,6 +56,12 @@
 	dest->ptr.v = NULL;
 }
 
+static inline void set_target_client(struct target *dest)
+{
+	dest->type = TARG_TYPE_CLIENT;
+	dest->ptr.v = NULL;
+}
+
 static inline void set_target_server(struct target *dest, struct server *s)
 {
 	dest->type = TARG_TYPE_SERVER;