Well, I think I got this CertificateRevocationList file right but PostgreSQL 8.1.8 seems to ignore it. At least if it is enough to host this root.crl file in the DB's data directory and restart postmaster.
OpenSSL says my test client's certificate was revoked but I still get a ssl-connection without complaints with pgAdmin.
Well ... checking again ... actually ... those CRL files aren't mentioned in the 8.1.x docu.
Maybe it isn't present in 8.1.x at all? There are 1001 ways to bust ones reputation ...