Precise event_base timer on Windows
Precise event_base timer on Windows

Summary: Without this the default libevent timing source on Windows is pretty horrible for pacing purposes. Even with this we can only seem to get pacing accuracy of around 3-5ms reliably, but this is much better than without.

Reviewed By: kvtsoy

Differential Revision: D38595163

fbshipit-source-id: 4f7993df0ebf87210371eaf1a5878960ebd447be

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