Removed old/buggy hardware workarounds from TimeSource

- Do not lock QueryPerformanceFrequency() to be done a single core
- Assume all systems running MPAR are having at least Windows XP (actually MPAR wont even work on XP as there is no WASAPI support)

http://msdn.microsoft.com/en-us/library/windows/desktop/dn553408(v=vs.85).aspx