create time format in EAs

[Björn JACKE]

Hi Jeremy,

looking at a770caed0ff66d it seems like you save the create time in NTTIME,
right?  Would it maybe be a good idea to save a timespec instead? One day we
might want to store create timestamps from posix clients in ns resolution which
won't be easily possible then. If we store a timespec with 64bit integers
instead we will be on the safe site and it doesn't hurt to to now. What do you
think?

Cheers
Björn