r17800: Start using struct timespec internally for file times

r17800: Start using struct timespec internally for file times
on the wire. This allows us to go to nsec resolution
for systems that support it. It should also now be
easy to add a correct "create time" (birth time)
for systems that support it (*BSD). I'll be watching
the build farm closely after this one for breakage :-).
Jeremy.
(This used to be commit 425280a1d23f97ef0b0be77462386d619f47b21d)