+ mapnik-write-colors-using-rgba-not-hex.patch (jonb)

When you use save_xml() the colors are written out in #RGB format
  which can not represent alpha information. The patch makes it save using
  the rgb()/rgba() strings.

include/mapnik/ptree_helpers.hpp

@@ -103,7 +103,7 @@ namespace mapnik {
     std::basic_ostream<charT, traits> &
     operator << ( std::basic_ostream<charT, traits> & s, const mapnik::color & c )
     {
-        std::string hex_string( c.to_hex_string() );
+        std::string hex_string( c.to_string() );
         s << hex_string;
         return s;
     }