Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/neteq/test/RTPencode.cc

 /*
  *  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 1810 matching lines @@
 }
 
 void stereoDeInterleave(int16_t* audioSamples, size_t numSamples) {
   int16_t* tempVec;
   int16_t* readPtr, *writeL, *writeR;
 
   if (numSamples == 0)
     return;
 
   tempVec = (int16_t*)malloc(sizeof(int16_t) * numSamples);
-  if (tempVec == NULL) {
+  if (tempVec == nullptr) {
     printf("Error allocating memory\n");
     exit(0);
   }
 
   memcpy(tempVec, audioSamples, numSamples * sizeof(int16_t));
 
   writeL = audioSamples;
   writeR = &audioSamples[numSamples / 2];
   readPtr = tempVec;
 
@@ skipping 34 matching lines @@
     memmove(ptrL + stride, ptrL, ptrR - ptrL);
 
     // copy from temp to left pointer
     memcpy(ptrL, temp, stride);
 
     // advance pointers
     ptrL += stride * 2;
     ptrR += stride;
   }
 }