support posix

1. posix pthread.h: pthread, pthread_barrier, pthread_cond, pthread_mutex, , pthread_rwlock, pthread_spin, etc
2. posix semaphore.h: sem_*
3. posix mqueue.h: mq_*
4. posix time.h: timer_*
5. to support posix, add tos_barrier, tos_bitmap, tos_rwlock, tos_stopwatch, change name of k_task_t from a char * pointer to a char array.
6. sample, see examples\posix
7. project, see board\TencentOS_tiny_EVB_MX_Plus\KEIL\posix

kernel/core/include/tos_robin.h

@@ -18,6 +18,8 @@
 #ifndef _TOS_ROBIN_H_
 #define  _TOS_ROBIN_H_
 
+__CDECLS_BEGIN
+
 #if TOS_CFG_ROUND_ROBIN_EN > 0u
 
 /**
@@ -50,5 +52,7 @@ __KNL__ void robin_sched(k_prio_t prio);
 
 #endif
 
+__CDECLS_END
+
 #endif /* _TOS_ROBIN_H_ */