avoid unused function compiler warning
avoid unused function compiler warning

gravitystorm/Ruby-Mapnik,gravitystorm/Ruby-Mapnik,mapnik/Ruby-Mapnik,mapnik/Ruby-Mapnik,mapnik/Ruby-Mapnik,gravitystorm/Ruby-Mapnik,gravitystorm/Ruby-Mapnik,mapnik/Ruby-Mapnik,gravitystorm/Ruby-Mapnik,gravitystorm/Ruby-Mapnik,mapnik/Ruby-Mapnik,mapnik/Ruby-Mapnik