This shows the full undo and redo stack, with all the metadata available
via the LOK API.

Also fix SfxUndoManager::GetRedoActionsInfo(), so it's easy to show the
undo/redo stack in linear time; and fix a use-after-free in lokdocview.

Change-Id: I66625ed453efa61b5738d99d7d1ad8f468908240
Reviewed-on: https://gerrit.libreoffice.org/27913Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>