spirit::karma based to_hex_string generator
+ to_string based on spirit::karma for completeness.
Merge branch 'master' of github.com:mapnik/mapnik into webp
catch boost::filesystem::directory_iterator::construct error and print warning rather than throwing exception - closes #1919 - refs mapbox/tilemill#1992
+ fix typo in grammar
iwyu
Merge branch 'master' of github.com:mapnik/mapnik into webp