sem_timedwait: The semaphore times out when the clock_REALTIME is used.

[y00575850]

	Dear Carlos,
When I use sem_timedwait, a time jump will cause the semaphore to time out. 
While I know that using CLOCK_REALTIME is POSIX-defined behavior, it doesn't 
fit the actual meaning of this function.To solve this problem, modify the 
sem_timedwait process, for example: add a switch control. 
Or add an interface that uses the Clock_MONOTONIC interface.

Best regards,
Yanchao