selftests/timers: Add leap-a-day test from timetest suite

This change adds the leap-a-day test which sets STA_INS and
STA_DEL each day to trigger leapseconds each day. It also
has a mode to jump the time to right before the end of the
day each iteration.

Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Tested-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>