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

fs/mmap/fs_munmap.c

@@ -200,11 +200,11 @@ int munmap(FAR void *start, size_t length)
       curr->length = length;
     }
 
-  sem_post(&g_rammaps.exclsem);
+  nxsem_post(&g_rammaps.exclsem);
   return OK;
 
 errout_with_semaphore:
-  sem_post(&g_rammaps.exclsem);
+  nxsem_post(&g_rammaps.exclsem);
   set_errno(errcode);
   return ERROR;
 }

fs/mmap/fs_rammap.c

@@ -229,7 +229,7 @@ FAR void *rammap(int fd, size_t length, off_t offset)
   map->flink  = g_rammaps.head;
   g_rammaps.head = map;
 
-  sem_post(&g_rammaps.exclsem);
+  nxsem_post(&g_rammaps.exclsem);
   return map->addr;
 
 errout_with_region: