fmax is not a valid POSIX macro

t/009_date_time_combination.t fails on some of my smokers, probably only with old perl versions (<= 5.20?):

    # Test No 5 died: fmax is not a valid POSIX macro at lib/DateTime/Format/Intl.pm line 3085
    # No tests run!

#   Failed test 'No tests run for subtest "DateTime::Format::Intl->new( en, {hour, minute, month, timeZoneName, weekday, year} )"'
#   at t/009_date_time_combination.t line 305.
fmax is not a valid POSIX macro at lib/DateTime/Format/Intl.pm line 3085
# Tests were run but no plan was declared and done_testing() was not seen.
# Looks like your test exited with 2 just after 8.
t/009_date_time_combination.t ...... 
Dubious, test returned 2 (wstat 512, 0x200)
Failed 1/8 subtests