mp3_afh: Detect both v1 and v2 tags.

mp3_afh: Detect both v1 and v2 tags.

Currently the mp3 audio format handler first looks at id3v2 tags and
ignores any id3v1 tags if a version 2 tag is present. This patch makes
it look at both types of tags, and combine the result if necessary.

We use the opportunity to also get rid of the file descriptor mess
in mp3_get_id3(). It is completely unnecessary as lib3d3tag can make
a id3_t structure from a memory buffer. We simply pass (a part of)
the memory map of the audio file and are done.

The techinfo field of struct audio_format_handler_info is changed
to show which tag versions the various tags were extracted. Possible
values are none, v1, v2 and v1+v2.