forgot to add warp.cpp as a source

src/build.py

@@ -152,6 +152,7 @@ source = Split(
     svg_path_parser.cpp
     svg_points_parser.cpp 
     svg_transform_parser.cpp
+    warp.cpp
     """   
     )
 

src/warp.cpp

@@ -27,6 +27,7 @@
 #include <mapnik/image_data.hpp>
 #include <mapnik/image_util.hpp>
 #include <mapnik/box2d.hpp>
+#include <mapnik/ctrans.hpp>
 
 // agg
 #include "agg_image_filters.h"
@@ -43,6 +44,8 @@
 #include "agg_image_accessors.h"
 #include "agg_renderer_scanline.h"
 
+namespace mapnik {
+
 void reproject_raster(raster &target, raster const& source,
                       proj_transform const& prj_trans,
                       double offset_x, double offset_y,
@@ -204,3 +207,4 @@ void reproject_raster(raster &target, raster const& source,
         }
     }
 }
+}// namespace mapnik