Track Number lost when greater than 255

I found a bug where the "track number" id3 field gets emptied whenever there's a value greater than 255. Most users won't run into this issue, but I'm using the audio module for a large media library, and storing things like series of podcasts will eventually result in higher numbers.

Normally if you set the ID3 of an MP3 with a number greater than 255, it will set the "track_number" field in id3v2 field correctly, but the "track" field in id3v1 will be empty. Although this is normal behavior in other software, the issue happens while READING the tags in the drupal module. The function audio_getid3.module/audio_read_id3tags() returns no track value when id3v1 "track" field is empty, even though there is a valid id3v2 field "track_number" value.

The fix is fairly simple. All we need to do is detect an empty "track", and fill it from id3v2's "track_number" field during tag reading. Attached is a patch against the latest 6.x-1.x-dev