Wait for at least “waitPeriodSecs”, don’t care if it takes a few milliseconds
longer. Optionally, return the real wakeup time “realWakeupTimeSecs”.
This call is useful if you want your code to release the cpu for a few
milliseconds, e.g., to avoid overloading the cpu in a spinning loop, and you
don’t care if the wait takes a few msecs longer than specified. If you do care,
use one of the other WaitSecs() variants! The other variants emphasize accuracy
of timed waits, even if this causes a high load on the processor.