Finish reverting "recheck_on_update" patch.
This reverts commit
c203d6cf8 and some follow-on fixes, completing the
task begun in commit
5d28c9bd7. If that feature is ever resurrected,
the code will look quite a bit different from this, so it seems best
to start from a clean slate.
The v11 branch is not touched; in that branch, the recheck_on_update
storage option remains present, but nonfunctional and undocumented.
Discussion: https://postgr.es/m/
20190114223409.3tcvejfhlvbucrv5@alap3.anarazel.de