D7521: [WIP] make use of foreign protocol

[Marco Martin]

mart reopened this revision.

REPOSITORY
  R108 KWin

REVISION DETAIL
  https://phabricator.kde.org/D7521

To: mart, #plasma, graesslin
Cc: luebking, graesslin, davidedmundson, plasma-devel, kwin, #kwin, ZrenBot, 
progwolff, lesliezhai, ali-mohamed, jensreuterberg, abetts, sebas, apol, mart, 
lukas