community/openscad: move from testing

(and moved library libspnav which is a dependency).

Note that all of the patches we are carrying for openscad exist upstream, (so we're just waiting for them to cut a release).

Some tests needed to be disabled for s390x... (not completely sure why, but I think I can live with that)

In the future, we should just disable s390x instead of disabling specific tests as it seems there's nobody with knowledge/interest in fixing the issues.