Three parts:
(1) The monkey patching of EncodedTextSpec to ignore encoding errors
when using latin1 as encoding.
This gets replaced with a new id3text function which makes sure
that any value passed to mutagen can be encoded with the selected
encoding
(2) MultiSpec monkey patch to not null terminate a list of strings.
While this is valid according to the spec mutagen decided to terminate
all strings (not only the text lists handled here). If this is a
problem it should be discussed upstream (mutagen).
(3) compatid3 which implemented id3v2.3 support and added some
additional frames.
This gets replaced with the id3v2.3 support implemented upstream.
The additional frames still get passed to mutagen and, to match
the previous implementation, update_to_v23() gets wrapped to
allow some v2.4 only frames.
The newly added id3v2.3 code depends on mutagen 1.22+
