Add support for reading WAV files that contain MP3 data.

[psobot]

We have the ability to decode MP3 files and the ability to decode WAV files, but not the ability to parse WAV files that contain MP3 data. This is supported by the WAV spec but is very rare.

This PR adds a wrapper PatchedWavAudioFormat that:

• Checks the headers of the WAV file to detect what compression is used therein
• If MP3 is detected, delegate to our existing MP3 parser
• If another unsupported format is detected, raise a descriptive error message

Includes fixture tests.

[hyperc54]

neat!
the test error is a bit mysterious