[FIX] undo: Make get_page_latest_version return the latest (not current) version, as it used to before current was stored in history, and pass this to use_version to do a simple rollback. Tested in combination with rolling back and editing - seems to work but watch out for side-effects.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@48209 b456876b-0849-0410-b77d-98878d47e9d5