Commit 578b2297 replaced it with a
concurrent "nextval" test.  That version does not detect PostgreSQL's
incompatibility with xlc 13.1.3, so bring back an OID-based test that
does.  Back-patch to v12, where that commit first appeared.

Discussion: https://postgr.es/m/20190707170035.GA1485546@rfd.leadboat.com