Introduce Mir display server
Merge branch 'master' of https://github.com/shiznix/unity-gentoo
[Saucy] Version bumps to mesa, mesa-mir and mir. Update net-im/friends-app Manifest
[Saucy] Introduce 'mir' USE flag for xorg-server to provide Xmir extension
[Saucy] Introduce mir-base/unity-system-compositor and 'mir' useflag for x11-misc/lightdm. Tidy up some missing metadata.xml files
[Saucy] version bumps