Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/uu.pyi

@@ -0,0 +1,16 @@
+import sys
+from typing import BinaryIO, Optional, Text, Union
+
+_File = Union[Text, BinaryIO]
+
+class Error(Exception): ...
+
+if sys.version_info >= (3, 7):
+    def encode(
+        in_file: _File, out_file: _File, name: Optional[str] = ..., mode: Optional[int] = ..., *, backtick: bool = ...
+    ) -> None: ...
+
+else:
+    def encode(in_file: _File, out_file: _File, name: Optional[str] = ..., mode: Optional[int] = ...) -> None: ...
+
+def decode(in_file: _File, out_file: Optional[_File] = ..., mode: Optional[int] = ..., quiet: int = ...) -> None: ...