Added a module with IPv6 utility methods

Simplifies the handling of bug Python issue 6926 [1].
(The IPPROTO_IPV6 is not usable on Windows)

[1] http://bugs.python.org/issue6926
Updated tests for Win32 threading speed

Either Win32 threads are really fast to start, or its time.time() method
is not as precise as in Linux, but main thread and started thread times
were equal.