windows: add GetSystemTimePreciseAsFileTime

https://msdn.microsoft.com/en-us/library/windows/desktop/hh706895(v=vs.85).aspx

Change-Id: I6e6a6642c041fad046ae7db725a27e7e94bfbfba
Reviewed-on: https://go-review.googlesource.com/39610
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2 files changed