D24966: KXmlGui: port away from KF5 deprecated API

[David Faure]

dfaure added a reviewer: jriddell.

REPOSITORY
  R263 KXmlGui

REVISION DETAIL
  https://phabricator.kde.org/D24966

To: dfaure, kossebau, elvisangelaccio, vkrause, jriddell
Cc: jriddell, kde-frameworks-devel, LeGast00n, GB_2, michaelh, ngraham, bruns