A simple script to convert ReplayGain tags to iTunNORM values.

It is (somewhat) based on Richard van den Berg's rg2sc script[1].

With a few improvements. It doesn't remove all other ID3 tags from mp3 files.
It handles both MP3 and MP4 files. There are only a few values iTunes looks at
in the iTunNORM tag to determine the volume adjustment. These are copied from
the existing iTunNORM tag. However, it doesn't handle the mp3gain default
APEv2 tags.

[1] http://www.vdberg.org/~richard/rg2sc.html