Hello Guix!

Here are a couple of patches adding the EasyTAG gnome package
https://wiki.gnome.org/Apps/EasyTAG.

EasyTAG depends on the libid3tag library and tries to find it using
pkg-config. I thought it'd be a good idea for the library to provide a
.pc file instead of manually telling EasyTAG where it is. It allows
cleaning up dependent packages a little, namely audacity and gmtp, what
do you think?

Thanks!
Pierre