Annoyingly, in Qt 5.5 we can no longer trigger shortcuts by replaying QKeyEvents (something that the Vi Mode - which stores and swallows all key events by default in case they are part of a Mapping and replays them if it turns out they weren't - depends on), so if we are stealing shortcuts, they will no longer be triggered e.g. pressing Ctrl+S will not save! This patch reworks the whole mechanism, moving from "swallow all QKeyEvents and maybe replay later" to "decide whether to swallow shortcuts, but if not, let Qt's shortcut handling system despatch the QShortcutOverride itself". This mostly fixes things, though we can't e.g. create a mapping that, when triggered, saves the document or triggers any of Kate's shortcuts, plus some other small edge cases :(

BUG:35333
REVIEW:D1894