COMP: propagate OTB_MAPNIK_SUPPORTS_API20 since it is used in UseOTB
COMP: propagate OTB_MAPNIK_SUPPORTS_API20 since it is used in UseOTB

orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB