Add support of unsynchronization

[n10v]

The only purpose of unsynchronisation is to make the ID3v2 tag as
compatible as possible with existing software and hardware. There is
no use in 'unsynchronising' tags if the file is only to be processed
only by ID3v2 aware software and hardware. Unsynchronisation is only
useful with tags in MPEG 1/2 layer I, II and III, MPEG 2.5 and AAC
files.

http://id3.org/id3v2.4.0-structure

[n10v]

Click 👍 if you need support of this feature. Click 👎 - if not.