#43 Use GetTickCount() on Windows for timing

[Mike Laughton]

We don’t want an accidental change of date and time (e.g. user switching the time zone) to interfere with the timing. Therefore, for all flavors of Windows we should use GetTickCount() system API which returns DWORD of milliseconds since last reboot. This is also easy to adapt to certain embedded systems.

(submitted on behalf of Alex)