Update libwebp to 0.4.0

third_party/libwebp/utils/quant_levels.h

 // Copyright 2011 Google Inc. All Rights Reserved.
 //
 // Use of this source code is governed by a BSD-style license
 // that can be found in the COPYING file in the root of the source
 // tree. An additional intellectual property rights grant can be found
 // in the file PATENTS. All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 // -----------------------------------------------------------------------------
 //
 // Alpha plane quantization utility
 //
 // Author:  Vikas Arora (vikasa@google.com)
 
 #ifndef WEBP_UTILS_QUANT_LEVELS_H_
 #define WEBP_UTILS_QUANT_LEVELS_H_
 
 #include <stdlib.h>
 
 #include "../webp/types.h"
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 extern "C" {
 #endif
 
 // Replace the input 'data' of size 'width'x'height' with 'num-levels'
 // quantized values. If not NULL, 'sse' will contain the sum of squared error.
 // Valid range for 'num_levels' is [2, 256].
 // Returns false in case of error (data is NULL, or parameters are invalid).
 int QuantizeLevels(uint8_t* const data, int width, int height, int num_levels,
                    uint64_t* const sse);
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 }    // extern "C"
 #endif
 
 #endif  /* WEBP_UTILS_QUANT_LEVELS_H_ */