Change-Id: Ica58d7b6c5865d02d0b286e5f9008c1d95189a00
This is the final step of the process described at <https://www.mediawiki.org/wiki/Separating_skins_from_core_MediaWiki>. Corresponding core change: Idfc38503. Change-Id: I84fcf7ce6385b8323544cafe6912a00f1886d20d