replaced usleep for windows

New: changed 2000 into a constant defined inline

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- Added functions to test usleep, msleep and sleep for accuracy. 
- Replaced windows usleep version with a non busy waiting high accuracy Version.
- Modified CALLBACK_ACCELERATOR_RATIO for windows because some systems need larger input buffer to work fine.

There are still issues when the framerate drops but that will be another worklist item ...

I fully understand that 'fetish'. Thats why I think that we have to work trough the remaining windows audio issues and on that way have to develop some metric to measure the actual environment the system is relying on. We'll continue to work in that direction ...