Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/marshal.pyi

@@ -0,0 +1,8 @@
+from typing import IO, Any
+
+version: int
+
+def dump(__value: Any, __file: IO[Any], __version: int = ...) -> None: ...
+def load(__file: IO[Any]) -> Any: ...
+def dumps(__value: Any, __version: int = ...) -> bytes: ...
+def loads(__bytes: bytes) -> Any: ...