unix, stmhal: Implement file.readinto() method.
Also, usocket.readinto(). Known issue is that .readinto() should be available
only for binary files, but micropython uses single method table for both
binary and text files.
diff --git a/py/stream.h b/py/stream.h
index 4cdc1b4..733c48e 100644
--- a/py/stream.h
+++ b/py/stream.h
@@ -25,6 +25,7 @@
*/
MP_DECLARE_CONST_FUN_OBJ(mp_stream_read_obj);
+MP_DECLARE_CONST_FUN_OBJ(mp_stream_readinto_obj);
MP_DECLARE_CONST_FUN_OBJ(mp_stream_readall_obj);
MP_DECLARE_CONST_FUN_OBJ(mp_stream_unbuffered_readline_obj);
MP_DECLARE_CONST_FUN_OBJ(mp_stream_unbuffered_readlines_obj);