Move file info from {audio} to {files}

Previous versions of Drupal weren't good about sharing the {files} table so the audio module stored it's files in {audio}. With Drupal 6 modules are supposed to play nice in the {files} table and keep their files there. We need to migrate the data from the {audio} table to the {files} table and then drop the columns from {audio}. It'll also mean touching a lot of the code because {audio} has colums named file_* while {files} uses file*. Touching this much code has me wishing that the audio module had unit tests...