Merge #9067: Fix exit codes

4441018 Every main()/exit() should return/use one of EXIT_ codes instead of magic numbers (UdjinM6)
bd0de13 Fix exit codes: - --help, --version etc should exit with 0 i.e. no error ("not enough args" case should still trigger an error) - error reading config file should exit with 1 (UdjinM6)