Added namespaces in the newly C++ified AEC code

webrtc/modules/audio_processing/aec/aec_core_neon.cc

Index: webrtc/modules/audio_processing/aec/aec_core_neon.cc
diff --git a/webrtc/modules/audio_processing/aec/aec_core_neon.cc b/webrtc/modules/audio_processing/aec/aec_core_neon.cc
index ba374b21ab8a452e88aa315240c47603d9978b57..baff9bed0e65bed314e4d550e3ffd7288fde2e4f 100644
--- a/webrtc/modules/audio_processing/aec/aec_core_neon.cc
+++ b/webrtc/modules/audio_processing/aec/aec_core_neon.cc
@@ -27,6 +27,8 @@ extern "C" {
 #include "webrtc/modules/audio_processing/aec/aec_rdft.h"
 }
 
+namespace webrtc {
+
 enum { kShiftExponentIntoTopMantissa = 8 };
 enum { kFloatExponentShift = 23 };
 
@@ -728,3 +730,4 @@ void WebRtcAec_InitAec_neon(void) {
   WebRtcAec_PartitionDelay = PartitionDelayNEON;
   WebRtcAec_WindowData = WindowDataNEON;
 }
+}  // namespace webrtc