D16735: Implement text_input_unstable_v3

[Roman Gilg]

romangg added a task: T9815: Improve touch/virtual keyboard.

REPOSITORY
  R127 KWayland

REVISION DETAIL
  https://phabricator.kde.org/D16735

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