microphone support

src/audio/OpenAL/AudioLayer.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/NullEmitter.hpp

src/audio/OpenAL/NullLayer.cpp

src/audio/OpenAL/NullLayer.hpp

src/audio/OpenAL/OpenALDevice.cpp

src/audio/OpenAL/OpenALLayer.cpp

src/audio/OpenAL/OpenALLayer.hpp

src/audio/OpenAL/OpenALSource.cpp

src/audio/OpenAL/OpenALSource.hpp

src/audio/OpenAL/PortAudioLayer.cpp

src/audio/OpenAL/PortAudioLayer.hpp

src/audio/OpenAL/README.txt

src/audio/OpenAL/example04.cpp

src/audio/OpenAL/example05.cpp