Further buildfarm testing shows that on the machines that are failing
ac75959c's test case, what we're actually getting from strtod("-infinity")
is a syntax error (endptr == value) not ERANGE at all.  This test case
is not worth carrying two sets of expected output for, so just remove it,
and revert commit b212245f's misguided attempt to work around the platform
dependency.

Discussion: https://postgr.es/m/E1h33xk-0001Og-Gs@gemulon.postgresql.org