This routine causes a thread to delay execution for a specific
    interval of time. This interval ends at the current time plus the
    specified interval. The routine will not return before the end
    of the interval is reached, but may return an arbitrary amount of
    time after the end of the interval is reached. This can be due to
    system load, thread priorities, and system timer granularity.

    Specifying an interval of zero (0) seconds and zero (0)
    nanoseconds is allowed and can be used to force the thread either
    to give up the processor or to deliver a pending cancelation
    request.

    The timespec structure contains the following two fields:

    o  tv_sec is an integral number of seconds.

    o  tv_nsec is an integral number of nanoseconds.