mapnik: support GDAL sources
mapnik: support GDAL sources

omniscale/magnacarto,omniscale/magnacarto,nebulon42/magnacarto,omniscale/magnacarto,kaiCu/magnacarto,nebulon42/magnacarto,nebulon42/magnacarto,omniscale/magnacarto,nebulon42/magnacarto,kaiCu/magnacarto