[MariaDB Packagers] MariaDB 10.2.15 release prep

Prep work for the MariaDB 10.2.15 release has begun. Expected release date is Thu 17 May 2018. Draft release notes and changelog: - https://mariadb.com/kb/en/mariadb-10215-release-notes/ - https://mariadb.com/kb/en/mariadb-10215-changelog/ As usual, the release notes and changelog are still in draft form at this time and will be updated prior to release. Thanks. -- Daniel Bartholomew, MariaDB Release Manager MariaDB | http://mariadb.com