update to mapnik v3.0.12-rc2
update to mapnik v3.0.12-rc2

mapnik/node-mapnik,tomhughes/node-mapnik,CartoDB/node-mapnik,CartoDB/node-mapnik,mapnik/node-mapnik,tomhughes/node-mapnik,mapnik/node-mapnik,CartoDB/node-mapnik,mapnik/node-mapnik,mapnik/node-mapnik,tomhughes/node-mapnik,tomhughes/node-mapnik,tomhughes/node-mapnik,CartoDB/node-mapnik,CartoDB/node-mapnik