Define the timespec64 structure and standard helper functions.

[ tglx: Make it 32bit only. 64bit really can map timespec to timespec64 ]
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>