IOCP.Windows: add LPDWORD, LPVOID, LPSTR
Capitalize SOCKET, to match Windows headers
Add conversion helpers for HANDLE and LPOVERLAPPED
IOCP.Utils: add withPtrLen
IOCP.Windows: add LPINT and PVOID
Import CancelIoEx unsafe (via the "dynamic" wrapper)
Add IOCP.Winsock.Bindings, currently a conversion of Winsock.c to Haskell

Right now, this will fail on Windows XP.  Need to see what error is produced
when WSASendMsg comes up missing.