remove warnings in audio directory and eventthread class

src/audio/audiofile.h

src/audio/audiolayer.h

src/audio/audioloop.h

src/audio/codecs/audiocodec.h

src/audio/dtmfgenerator.cpp

src/audio/ringbuffer.cpp

src/audio/ringbuffer.h

src/audio/tonelist.h

src/eventthread.cpp