VAD refactor: Mode changed to "int".

As part of style this CL includes changing the input aggressiveness mode from int16_t to int. No other style changes made.
Impact on:
- Audio Processing: Changed return value on MapSetting().
- Function test in audio_conference_mixer already uses int. No action.
- NetEq: Function pointer changes and input parameter changes in SetVADMode() and SetVADModeInternal().
- Audio Coding: Uses enum ACMVADMode which is type independent.
- VAD: Two unit tests.

TESTS=vad_unittests, neteq_unittests, audioproc_unittest
Review URL: https://webrtc-codereview.appspot.com/373001

git-svn-id: http://webrtc.googlecode.com/svn/trunk@1544 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/src/modules/audio_processing/voice_detection_impl.cc b/src/modules/audio_processing/voice_detection_impl.cc
index 49aac2e..e1c0f0e 100644
--- a/src/modules/audio_processing/voice_detection_impl.cc
+++ b/src/modules/audio_processing/voice_detection_impl.cc
@@ -1,5 +1,5 @@
 /*
- *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *  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
@@ -23,7 +23,7 @@
 typedef VadInst Handle;
 
 namespace {
-WebRtc_Word16 MapSetting(VoiceDetection::Likelihood likelihood) {
+int MapSetting(VoiceDetection::Likelihood likelihood) {
   switch (likelihood) {
     case VoiceDetection::kVeryLowLikelihood:
       return 3;