Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/idna/compat.py

@@ -0,0 +1,13 @@
+from .core import *
+from .codec import *
+from typing import Any, Union
+
+def ToASCII(label: str) -> bytes:
+    return encode(label)
+
+def ToUnicode(label: Union[bytes, bytearray]) -> str:
+    return decode(label)
+
+def nameprep(s: Any) -> None:
+    raise NotImplementedError('IDNA 2008 does not utilise nameprep protocol')
+