D13510: Add XDG WM Base support to our XDGShell API

[David Edmundson]

davidedmundson removed a dependency: D13530: Add XDG WmBase support.

REPOSITORY
  R127 KWayland

REVISION DETAIL
  https://phabricator.kde.org/D13510

To: davidedmundson, #kwin
Cc: romangg, zzag, kde-frameworks-devel, michaelh, ngraham, bruns