Update some cmoments

include/nuttx/syslog/syslog.h

@@ -214,6 +214,10 @@ int syslog_flush(void);
  *   equivalent to vsyslog() except that the pre-process priority filtering
  *   has already been performed and, hence, there is no priority argument.
  *
+ *   NOTE:  The va_list parameter is passed by reference.  That is because
+ *   the va_list is a structure in some compilers and passing of structures
+ *   in the NuttX sycalls does not work.
+ *
  ****************************************************************************/
 
 int _vsyslog(FAR const IPTR char *src, FAR va_list *ap);