replaced usleep for windows

- 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 ...

Is there anyway to determine this more dynamically? In other words for machines that require more buffering determine that, and allow other devices to have less buffering? I won't hold up merge for this, but merely asking.