r21714: Change the VFS interface to use struct timespec

r21714: Change the VFS interface to use struct timespec
for utimes - change the call to ntimes. This preserves
nsec timestamps we get from stat (if the system supports
it) and only maps back down to usec or sec resolution
on time set. Looks bigger than it is as I had to move
lots of internal code from using time_t and struct utimebuf
to struct timespec.
Jeremy.