-XXX could add setting of *valueptr to all the OK returns; seems doable here, the Q
- is: what effect would it have at config-file level. domain_data & local_part_data
- would get filled in... might anyone be checking it for emptiness? I think the docs
- do not say "will be empty otherwise", so that seems ok.
-XXX WORRY: we get new caching of named-list match results. Is that cache checked
- for the key being matched?