Added StructStat nanosecond precision fields.

Since Linux 2.6 the kernel supports nanosecond precision
(with timespec struct) for times of: last access, last
modification and last status change in stat struct.

Test: CtsLibcoreTestCases
Bug: 62949898
Change-Id: Ie3f13f621bc64dd20f01fdc0c10906f02f41909c
5 files changed