Much as we would like to, we have to live for the time being with

Much as we would like to, we have to live for the time being with
broken objectclass and attributetype definitions where the OID is
missing.  The implementation of OIDmacros was making this impossible.
This change tries to restore the old behaviour, while preserving the
new feature.  Note that part of the restored behaviour lets OIDs that
are not in the numericoid format get through.  We may lose this, but
then we need to fix some of the sample provided schemas, notably
pilot.schema.