Moved the AEC C code to be built using C++

webrtc/modules/audio_processing/aec/echo_cancellation.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE 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.
  */
 
@@ skipping 35 matching lines @@
 
 typedef struct {
   AecLevel rerl;
   AecLevel erl;
   AecLevel erle;
   AecLevel aNlp;
 } AecMetrics;
 
 struct AecCore;
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /*
  * Allocates the memory needed by the AEC. The memory needs to be initialized
  * separately using the WebRtcAec_Init() function. Returns a pointer to the
  * object or NULL on error.
  */
 void* WebRtcAec_Create();
 
 /*
  * This function releases the memory allocated by WebRtcAec_Create().
  *
@@ skipping 161 matching lines @@
 // Returns a pointer to the low level AEC handle.
 //
 // Input:
 //  - handle                    : Pointer to the AEC instance.
 //
 // Return value:
 //  - AecCore pointer           : NULL for error.
 //
 struct AecCore* WebRtcAec_aec_core(void* handle);
 
-#ifdef __cplusplus
-}
-#endif
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC_ECHO_CANCELLATION_H_