Added stub for Python 2's _threading_local (#1461)

stdlib/2/_threading_local.pyi

@@ -0,0 +1,14 @@
+# Source: https://hg.python.org/cpython/file/2.7/Lib/_threading_local.py
+from typing import Any, List
+
+__all__: List[str]
+
+class _localbase(object): ...
+
+class local(_localbase):
+    def __getattribute__(self, name: str) -> Any: ...
+    def __setattr__(self, name: str, value: Any) -> None: ...
+    def __delattr__(self, name: str) -> None: ...
+    def __del__(self) -> None: ...
+
+def _patch(self: local) -> None: ...