Ensured that all files in APM are using the webrtc namespace

This CL adds namespaces to those files remaining within APM that do not
have any such.

BUG=webrtc:5298

Change-Id: I710b3d2a3644bea9d4bdffef0d77883b30303338
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/171111
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30850}

modules/audio_processing/vad/noise_gmm_tables.h

@@ -13,6 +13,8 @@
 #ifndef MODULES_AUDIO_PROCESSING_VAD_NOISE_GMM_TABLES_H_
 #define MODULES_AUDIO_PROCESSING_VAD_NOISE_GMM_TABLES_H_
 
+namespace webrtc {
+
 static const int kNoiseGmmNumMixtures = 12;
 static const int kNoiseGmmDim = 3;
 
@@ -74,4 +76,7 @@ static const double kNoiseGmmWeights[kNoiseGmmNumMixtures] = {
     -1.79789356118641e+01, -1.42830169160894e+01, -1.56500228061379e+01,
     -1.83124990950113e+01, -1.69979436177477e+01, -1.12329424387828e+01,
     -1.41311785780639e+01, -1.47171861448585e+01, -1.35963362781839e+01};
+
+}  // namespace webrtc
+
 #endif  // MODULES_AUDIO_PROCESSING_VAD_NOISE_GMM_TABLES_H_