Squashed commit of the following:

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

    sched/semaphore:  Rename all internal private functions from sem_xyz to nxsem_xyz.  The sem_ prefix is (will be) reserved only for the application semaphore interfaces.

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

    sched/semaphore:  Rename sem_tickwait() to nxsem_tickwait() so that it is clear this is an internal OS function.

    sched/semaphoate:  Rename sem_reset() to nxsem_reset() so that it is clear this is an internal OS function.

drivers/syslog/ramlog.c

@@ -694,9 +694,9 @@ int ramlog_register(FAR const char *devpath, FAR char *buffer, size_t buflen)
     {
       /* Initialize the non-zero values in the RAM logging device structure */
 
-      sem_init(&priv->rl_exclsem, 0, 1);
+      nxsem_init(&priv->rl_exclsem, 0, 1);
 #ifndef CONFIG_RAMLOG_NONBLOCKING
-      sem_init(&priv->rl_waitsem, 0, 0);
+      nxsem_init(&priv->rl_waitsem, 0, 0);
 
       /* The rl_waitsem semaphore is used for signaling and, hence, should
        * not have priority inheritance enabled.

drivers/syslog/syslog_device.c

@@ -405,7 +405,7 @@ int syslog_dev_initialize(FAR const char *devpath, int oflags, int mode)
 
   /* The SYSLOG device is open and ready for writing. */
 
-  sem_init(&g_syslog_dev.sl_sem, 0, 1);
+  nxsem_init(&g_syslog_dev.sl_sem, 0, 1);
   g_syslog_dev.sl_holder = NO_HOLDER;
   g_syslog_dev.sl_state  = SYSLOG_OPENED;
   return OK;