GNOME Music in GTK+ 3.8

We ported GNOME Music to be usable on GTK+ 3.8, so that users using stable versions of their distributions could use it 😀

Note that compatibility with GTK+ 3.8 will be removed on the next cycle, GNOME 3.12.

We tested it to work on Ubuntu 13.04 (with the GNOME PPA’s), Fedora 19, openSUSE 12.3 (with GNOME:STABLE:3.8 repository), Debian Sid (Yes, that’s not stable but Wheezy’s GTK+ is too old) and Arch Linux.