libxkbcommon-0.3.0 was released and is now required for mpv[wayland]: https://github.com/mpv-player/mpv/commit/c0b8c35e3ba858ef8e5e47ebc45ccaa88ef86348
x11-libs/libxkbcommon-0.3.1 is in x11 overlay, please commit to portage.
+*libxkbcommon-0.3.1 (11 Jun 2013) + + 11 Jun 2013; Kacper Kowalik <xarthisius@gentoo.org> + +libxkbcommon-0.3.1.ebuild: + Version bump wrt #470076 by Nikoli <nikoli@lavabit.com>