Silence `-Wundefined-var-template` warnings in enumeration.hpp
Silence `-Wundefined-var-template` warnings in enumeration.hpp

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