Operational note: possible infinite loop in today's HEAD testing

If you run any PG buildfarm critters that are configured with
--enable-tap-tests, you might want to check to see if they're caught
in an infinite loop in pgbench :-(.  If so, just kill -9 that process,
and the next run should recover OK.

The cause is a platform-dependent bug introduced in commit 12788ae49
and fixed in 9779bda86.

A look through the buildfarm status says that the only members using
--enable-tap-tests that haven't reported in successfully despite the bug
are hamster, jacana, and topminnow.  But I'm sending this out more
widely just in case I missed somebody's machine.

(Andrew: I wonder if we should have a sanity limit on how long buildfarm
runs are allowed to take.  Not sure what to put the limit at, though.)

            regards, tom lane