Introduce undocumented option -d to dump parsed zonetab file contents
and add a "baseline" target along with instructions to share/zoneinfo.
Baseline file is not installed in the system, and serves only as a check for when zoneinfo or tzsetup is updated.
It could be located under usr.sbin/tzsetup/, but zoneinfo updates are much more frequent and IMO share/zoneinfo (NOTE, only in src tree, it's not installed) is better location to not forget about this check.
Do this before changes in D39606 land to make sure it doesn't break anything it's not supposed to.
Intended to catch unexpected changes (like Iceland being listed under Africa that D39606 should fix).
Philip, does having a baseline inside share/zoneinfo/ make sense to you?