of rule uses, but also in test_filter_mra()

Don't yet list ordering rules yet, these require special attention (and
hence are not marked MR_EXT yet)

Also add uses where mr is the attribute's equality rule.

the syntax's assertion syntax.

Use attribute's cname not oid in matching rule uses

add {create,modify}Timestamp to subschema subentry (SHOULD per RFC2251; use server startup time to be conservative)

fix extendedMatch and approx hfilter andling; get rid of subtree_cond (argh, need to trim it from config and docs ...)

added referral support to back-{ldap,meta}; need to allow send_serch_reference() handle NULL entry pointer

let caller log it if they care.