This CL pulls together similar time conversion functions and adds
conversions between `FILETIME`s and `timespec`s.
Bug: crashpad:206
Change-Id: I1d9b1560884ffde2364af0092114f82e1534ad1c
Reviewed-on: https://chromium-review.googlesource.com/752574
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>