media-sound/denemo: bump to version 2.3.0

media-sound/denemo: bump to version 2.3.0

- bump to EAPI=7
- inherit xdg instead of xdg-utils
- rename doc USE flag to gtk-doc
- add subslot modifier for media-libs/aubio and media-sound/fluidsynth

The bug below blocks this update for multilib machines and needs to be
merged first!
Bug: https://bugs.gentoo.org/691274

Closes: https://bugs.gentoo.org/691920
Package-Manager: Portage-2.3.71, Repoman-2.3.17
Signed-off-by: Bernd Waibel <waebbl@gmail.com>
Closes: https://github.com/gentoo/gentoo/pull/12704
Signed-off-by: Joonas Niilola <juippis@gentoo.org>