Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/@python2/cPickle.pyi

@@ -0,0 +1,26 @@
+from typing import IO, Any, List
+
+HIGHEST_PROTOCOL: int
+compatible_formats: List[str]
+format_version: str
+
+class Pickler:
+    def __init__(self, file: IO[str], protocol: int = ...) -> None: ...
+    def dump(self, obj: Any) -> None: ...
+    def clear_memo(self) -> None: ...
+
+class Unpickler:
+    def __init__(self, file: IO[str]) -> None: ...
+    def load(self) -> Any: ...
+    def noload(self) -> Any: ...
+
+def dump(obj: Any, file: IO[str], protocol: int = ...) -> None: ...
+def dumps(obj: Any, protocol: int = ...) -> str: ...
+def load(file: IO[str]) -> Any: ...
+def loads(str: str) -> Any: ...
+
+class PickleError(Exception): ...
+class UnpicklingError(PickleError): ...
+class BadPickleGet(UnpicklingError): ...
+class PicklingError(PickleError): ...
+class UnpickleableError(PicklingError): ...