Added support for GetSystemTime() and SetSystemTime()

[GetSystemTime() documentation](http://msdn.microsoft.com/en-gb/library/windows/desktop/ms724390(v=vs.85).aspx)
[SetSystemTime() documentation](http://msdn.microsoft.com/en-gb/library/windows/desktop/ms724942(v=vs.85).aspx)
[SYSTEMTIME struct documentation](http://msdn.microsoft.com/en-gb/library/windows/desktop/ms724950(v=vs.85).aspx)

Tested on a Windows Server 2012 R2 machine.