Updated mediawiki/extensions
Project: mediawiki/extensions/UserGroups  8361acb9d2ad805788e54b5cbc795e8379c5d560

Revert "Revert "Add core extension files/classes""

This reverts commit 6cbea16858c1b298ea994072ebceab0570dd207e.

Change-Id: I6960c70ed709b60292ec6c6df14827dfd6adf665