"env EXTRA_REGRESS_OPTS=--temp-config=SOMEFILE make check" appends the
contents of SOMEFILE to the test cluster's postgresql.conf. I want a similar
feature for TAP suites and other non-pg_regress suites. (My immediate use
case is to raise authentication_timeout and wal_sender_timeout on my buildfarm
animals, which sometimes fail at the defaults.) I'm thinking to do this by
recognizing the PG_TEST_TEMP_CONFIG environment variable as a
whitespace-separated list of file names for appending to postgresql.conf.
