Remove unuseful audio code

src/audio/OpenAL/AudioLayer.cpp

src/audio/OpenAL/AudioLayer.hpp

src/audio/OpenAL/AudioManager.hpp

src/audio/OpenAL/AudioManagerImpl.cpp

src/audio/OpenAL/AudioManagerImpl.hpp

src/audio/OpenAL/Context.cpp

src/audio/OpenAL/Context.hpp

src/audio/OpenAL/Device.cpp

src/audio/OpenAL/Device.hpp

src/audio/OpenAL/Emitter.cpp

src/audio/OpenAL/Emitter.hpp

src/audio/OpenAL/Makefile.am

src/audio/OpenAL/MicEmitter.cpp

src/audio/OpenAL/MicEmitter.hpp

src/audio/OpenAL/Null/NullContext.cpp

src/audio/OpenAL/Null/NullContext.hpp

src/audio/OpenAL/Null/NullDevice.cpp

src/audio/OpenAL/Null/NullDevice.hpp

src/audio/OpenAL/Null/NullEmitter.hpp

src/audio/OpenAL/Null/NullLayer.cpp