add code comment about visibility after https://github.com/joyent/node/commit/bd8a5755dceda415eee147bc06574f5a30abb0d0#commitcomment-5686345
add code comment about visibility after https://github.com/joyent/node/commit/bd8a5755dceda415eee147bc06574f5a30abb0d0#commitcomment-5686345

stefanklug/node-mapnik,tomhughes/node-mapnik,tomhughes/node-mapnik,mapnik/node-mapnik,Uli1/node-mapnik,tomhughes/node-mapnik,tomhughes/node-mapnik,mapnik/node-mapnik,MaxSem/node-mapnik,Uli1/node-mapnik,langateam/node-mapnik,stefanklug/node-mapnik,mapnik/node-mapnik,CartoDB/node-mapnik,CartoDB/node-mapnik,langateam/node-mapnik,langateam/node-mapnik,MaxSem/node-mapnik,CartoDB/node-mapnik,CartoDB/node-mapnik,stefanklug/node-mapnik,langateam/node-mapnik,CartoDB/node-mapnik,mapnik/node-mapnik,stefanklug/node-mapnik,Uli1/node-mapnik,langateam/node-mapnik,MaxSem/node-mapnik,mapnik/node-mapnik,Uli1/node-mapnik,MaxSem/node-mapnik,tomhughes/node-mapnik