Print compiler, options at end of CMake
Fix some compiler warnings
Forward AudioTestData submodule to latest master
Fix typo in help for --channels option
Assert return value of AudioSettings setters

Also add corresponding unit/integration tests.
Treat unsupported WAVE audio formats as error
Introduce types for channel counts, sample sizes, etc.
Analysis error now shows channel & frame

Also the distortion analysis method is a bit more robust and uses
per-channel history.
Add BitDepth enum, setting to AudioSettings class

Unit tests added as well.
Add PcmSampleBuffer class
Option for bit-depth (for raw PCM files)
Audiofile SampleSource uses PcmSampleBuffer
PCM SampleSource uses PcmSampleBuffer
WAVE SampleSource supports multiple bitrates (experimental)
Add --endian option for raw PCM data
Remove code for PCM sample conversion from SampleBuffer

No longer necessary now that we have PcmSampleBuffer class.