Fix for newer versions of rrdtool.
Fix for newer versions of rrdtool.
jprochazka/adsb-receiver,jprochazka/adsb-feeder,jprochazka/adsb-receiver,jprochazka/adsb-receiver,jprochazka/adsb-receiver,jprochazka/adsb-feeder,jprochazka/adsb-feeder,jprochazka/adsb-feeder,jprochazka/adsb-receiver,jprochazka/adsb-feeder