Fix 24bit/4byte format when used in Linux

As pointed out in #16, Linux ALSA/PulseAudio uses a different data representation than Windows when dealing with 24bit samples in 4 byte containers (AE_FMT_S24NE4, AE_FMT_S24BE4, AE_FMT_S24LE4) . This patch set introduces two distinct groups of formats. One that uses the upper 3 bytes (Windows) and on that uses the lower 3 bytes (Linux)  to carry the audio data. The new formats are named AE_FMT_S24xE4H and AE_FMT_S24xE4L. The native formats ALSA:SND_PCM_FORMAT_S24 and PulseAudio:PA_SAMPLE_S24_32xE are now mapped to AE_FMT_S24NE4L.