Update to agda-2.8.0, but there are broken files

[andreasabel]

This repo didn't build anymore. Anton @csetzer you made some effort 4 years ago to keep this code alive. So I tried to make it work with latest Agda. We should not have projects in the agda organization that do not build; I have been using these to agda-attic. However, our JFP paper links to agda/ooAgda so maybe we should keep it alive.