Test program for duplicating sockets in windows
Reproduce case for crash in dup() on windows
Use wsaduplicatesocket instead of dup on windows to avoid crashes.

http://curl.haxx.se/mail/curlpython-2013-12/0012.html

Reported by Gisle Vanem.
Add a const
Merge pull request #106 from p-push/winsockdup

Use wsaduplicatesocket instead of dup on windows to avoid crashes