Changed Diff module to behave like Revisions

Hello,

I do not know how to make diff files, but you should be able to manually work this change into your diff.module.

This is a simple change to give a more Revisions like appearance to the diff layout. The current revision is labelled as published while any revisions before the current revision are labelled archive and any after the current are labelled draft.

Maybe someone can massage this into any other changes made to the diff.module.

Thanks.