These parts were identical duplicates, so I removed them
and made AudReader depend on ImaAdpcmReader instead.
Applied some style fixes while I was at it.
- Where it is accessible, use the length of the stream to presize the MemoryStream to the correct size.
- Instead of copying out the result via ToArray, grab the underlying buffer via GetBuffer and use that to create the sound source.
This avoids extraneous copying of the array containing the audio.
