afh: Introduce audio_format_names[].

afh: Introduce audio_format_names[].

This removes .name of struct audio_format in favor of an array of
strings. This will allow us to make afl[] a constant array of pointers,
some of which may be NULL to indicate that the audio format was not
compiled in.

This temporarily duplicates the list of audio formats. The second
list will be removed in a subsequent commit.