This helps write scripts like this:

    optstring=$(varnishd -x optstring)

    while getopts $optstring opt
    do
        case $opt in
        n)
            # handle $OPTARG
            ;;
        # handle other options
        *)
            # ignore unneeded options
            ;;
        esac
    done

    varnishd "$@"

Otherwise if optstring is not kept in sync, getopts will stop processing
options if it encounters one that is not specified.