Replace NULL with nullptr in all C++ files.

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

Index: webrtc/modules/audio_coding/neteq/test/RTPchange.cc
diff --git a/webrtc/modules/audio_coding/neteq/test/RTPchange.cc b/webrtc/modules/audio_coding/neteq/test/RTPchange.cc
index 54395c026afc072d686b8b46a34b50ef2818c850..75aa5ba4e62110006e60fe54a9b1103632961cf8 100644
--- a/webrtc/modules/audio_coding/neteq/test/RTPchange.cc
+++ b/webrtc/modules/audio_coding/neteq/test/RTPchange.cc
@@ -48,7 +48,7 @@ int main(int argc, char* argv[]) {
   // Read all statistics and insert into map.
   // Read first line.
   char temp_str[100];
-  if (fgets(temp_str, 100, stat_file) == NULL) {
+  if (fgets(temp_str, 100, stat_file) == nullptr) {
     printf("Failed to read timing file %s\n", argv[2]);
     return -1;
   }
@@ -70,7 +70,7 @@ int main(int argc, char* argv[]) {
 
   // Read file header and write directly to output file.
   char first_line[FIRSTLINELEN];
-  if (fgets(first_line, FIRSTLINELEN, in_file) == NULL) {
+  if (fgets(first_line, FIRSTLINELEN, in_file) == nullptr) {
     printf("Failed to read first line of input file %s\n", argv[1]);
     return -1;
   }