Support revisioning and workflow modules to remove unpublished nodes from broken link report

Once a page gets unpublished, it should be removed from the broken link report through hook_node_update. It appears that currently linkchecker does not work with Revisioning (6.x-3.15) and Workflow (6.x-1.5) as nodes that get unpublished stay in the report. It is irrelevant if the unpublish action is triggered through a workflow action or directly on the node edit "publishing options".