Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/quopri.pyi

@@ -0,0 +1,6 @@
+from typing import BinaryIO
+
+def encode(input: BinaryIO, output: BinaryIO, quotetabs: int, header: int = ...) -> None: ...
+def encodestring(s: bytes, quotetabs: int = ..., header: int = ...) -> bytes: ...
+def decode(input: BinaryIO, output: BinaryIO, header: int = ...) -> None: ...
+def decodestring(s: bytes, header: int = ...) -> bytes: ...