Sigh, I pushed an infinite-loop test in HEAD

Slower PG buildfarm members might find that the test I added in commit
b3427dade14cc31eb48740bc9ea98b5954470b24 proves to be an infinite loop.
If your critter would have started a run in the last two hours or so,
please check it and see if there's a postgres process that's consuming
100% CPU and has been for more than a minute or so.  If so, "kill -TERM"
should be enough to fix it.  I've pushed a correction, so tests starting
in future should be fine.

Sorry about that :-(

            regards, tom lane