add a asdl bytes type, so Bytes.s be properly typechecked
diff --git a/Include/asdl.h b/Include/asdl.h
index 9bb0697..42bbbf8 100644
--- a/Include/asdl.h
+++ b/Include/asdl.h
@@ -3,6 +3,7 @@
 
 typedef PyObject * identifier;
 typedef PyObject * string;
+typedef PyObject * bytes;
 typedef PyObject * object;
 
 /* It would be nice if the code generated by asdl_c.py was completely