add global, per backend and per op_ndn time/size soft, hard and to-be-checked limits (exploited by back-ldbm); see slapd.conf(5) for details

Likely should have a general solution to this.

case-Exact/Ignore-Substrings-Match/Filter/Indexer with common code for
the caseExact and caseIgnore cases

but can really be removed.

followed by stripping of characters with 8th bit set. The normalization
is needed to make exact match imply approx match.