[NaCl SDK] nacl_io: fix TTY warning messages when using naclterm/hterm.

native_client_sdk/src/libraries/nacl_io/log.h

 /* Copyright (c) 2013 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file. */
 
 #ifndef LIBRARIES_NACL_IO_LOG_H_
 #define LIBRARIES_NACL_IO_LOG_H_
 
 #include "sdk_util/macros.h"
 
 #define LOG_PREFIX "nacl_io: "
 
 #if NACL_IO_LOGGING
 #define LOG_TRACE(format, ...) \
   nacl_io_log(LOG_PREFIX format "\n", ##__VA_ARGS__)
 #else
 #define LOG_TRACE(format, ...)
 #endif
 
 #define LOG_ERROR(format, ...) \
   nacl_io_log(LOG_PREFIX "error: " format "\n", ##__VA_ARGS__)
 
+#define LOG_WARN(format, ...) \
+  nacl_io_log(LOG_PREFIX "warning: " format "\n", ##__VA_ARGS__)
+
 EXTERN_C_BEGIN
 
 /*
  * Low level logging function for nacl_io log messages.
  *
  * This function sends its output directly to the IRT standard out
  * file descriptor, which by default will apear on the standard out
  * or chrome or sel_ldr.
  */
 void nacl_io_log(const char* format, ...) PRINTF_LIKE(1, 2);
 
 EXTERN_C_END
 
 #endif  /* LIBRARIES_NACL_IO_LOG_H_ */