Setting language field for mp3s using generic interface does not convert 'English' to 'eng'

[IJabz]

From https://java.net/jira/browse/JAUDIOTAGGER-410

If using the id3 interface you know that if you want to set the language to English you need to use the isocode 'eng', but its not clear you have to do this when using generic interface. In fact although I write 'English' rather than 'eng' for Flac, Mp4, Vorbis ectera it seems that Picard always writes 'eng', not sure who is right here.