sddm: Bump to version 0.18
Summary:
Bump sddm to version 0.18 based on the recipe in meta-qt5-extra and also move sddm into it's own directory.
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewers: vkrause
Reviewed By: vkrause
Differential Revision: https://phabricator.kde.org/D18540