Squashed commit of the following:

sched/semaphore:  Add nxsem_post() which is identical to sem_post() except that it never modifies the errno variable.  Changed all references to sem_post in the OS to nxsem_post().

    sched/semaphore:  Add nxsem_destroy() which is identical to sem_destroy() except that it never modifies the errno variable.  Changed all references to sem_destroy() in the OS to nxsem_destroy().

    libc/semaphore and sched/semaphore:  Add nxsem_getprotocol() and nxsem_setprotocola which are identical to sem_getprotocol() and set_setprotocol() except that they never modifies the errno variable.  Changed all references to sem_setprotocol in the OS to nxsem_setprotocol().  sem_getprotocol() was not used in the OS

libc/pthread/pthread_barrierinit.c

@@ -95,7 +95,7 @@ int pthread_barrier_init(FAR pthread_barrier_t *barrier,
     }
   else
     {
-      nxsem_init(&barrier->sem, 0, 0);
+      sem_init(&barrier->sem, 0, 0);
       barrier->count = count;
     }
 

libc/pthread/pthread_barrierwait.c

@@ -109,7 +109,7 @@ int pthread_barrier_wait(FAR pthread_barrier_t *barrier)
 
   /* Find out how many threads are already waiting at the barrier */
 
-  ret = nxsem_getvalue(&barrier->sem, &semcount);
+  ret = sem_getvalue(&barrier->sem, &semcount);
   if (ret != OK)
     {
       sched_unlock();
@@ -125,7 +125,7 @@ int pthread_barrier_wait(FAR pthread_barrier_t *barrier)
       while (semcount < 0)
         {
           (void)sem_post(&barrier->sem);
-          (void)nxsem_getvalue(&barrier->sem, &semcount);
+          (void)sem_getvalue(&barrier->sem, &semcount);
         }
 
       /* Then return PTHREAD_BARRIER_SERIAL_THREAD to the final thread */

libc/pthread/pthread_condinit.c

@@ -81,7 +81,7 @@ int pthread_cond_init(FAR pthread_cond_t *cond, FAR const pthread_condattr_t *at
    * initial count = 0
    */
 
-  else if (nxsem_init((FAR sem_t *)&cond->sem, 0, 0) != OK)
+  else if (sem_init((FAR sem_t *)&cond->sem, 0, 0) != OK)
     {
       ret = EINVAL;
     }