Move the AudioDecoder interface out of NetEq

It belongs with the codecs, next to the AudioEncoder interface.

R=henrik.lundin@webrtc.org, kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/27309004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7798 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/neteq/decoder_database.h

@@ -15,15 +15,12 @@
 
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/common_types.h"  // NULL
-#include "webrtc/modules/audio_coding/neteq/interface/audio_decoder.h"
+#include "webrtc/modules/audio_coding/neteq/audio_decoder_impl.h"
 #include "webrtc/modules/audio_coding/neteq/packet.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 
-// Forward declaration.
-class AudioDecoder;
-
 class DecoderDatabase {
  public:
   enum DatabaseReturnCodes {