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

graphics/nxterm/nxterm_sem.c

@@ -107,7 +107,7 @@ int nxterm_sempost(FAR struct nxterm_state_s *priv)
   /* Then let go of it */
 
   priv->holder = NO_HOLDER;
-  return sem_post(&priv->exclsem);
+  return nxsem_post(&priv->exclsem);
 }
 
 #endif /* CONFIG_DEBUG_FEATURES */