expressions_test: change properties_type to std::map
expressions_test: change properties_type to std::map

naturalatlas/mapnik,mapnik/mapnik,naturalatlas/mapnik,tomhughes/mapnik,lightmare/mapnik,mapnik/mapnik,lightmare/mapnik,mapnik/mapnik,naturalatlas/mapnik,tomhughes/mapnik,tomhughes/mapnik,lightmare/mapnik,lightmare/mapnik,tomhughes/mapnik,naturalatlas/mapnik,mapnik/mapnik