gistfile1.txt

produces (but try changing bbox):

```
before: box2d(-180,-60,180,60)
after back: box2d(-20037508.34278924,-8399737.889818359,20037508.34278924,8399737.889818355)
after forward: box2d(-180,-60.00000000000001,180,59.99999999999999)
```

transformer_glitch.cpp

#include <mapnik/projection.hpp>
#include <mapnik/proj_transform.hpp>

/*
clang++ -o t trans.cpp `mapnik-config --cflags` -lmapnik;./t
*/

int main()
{

    mapnik::projection merc =  mapnik::projection("+init=epsg:3857 +over");
    mapnik::projection wgs84 = mapnik::projection("+init=epsg:4326 +over");
    mapnik::proj_transform transformer(merc, wgs84);
    
    mapnik::box2d<double> bb(-180,-60,180,60);
    
    std::clog << "before: " << bb << "\n";
    
    if (!transformer.backward(bb))
        std::clog << "proj backward failed!\n";
    
    std::clog << "after back: " << bb << "\n";
    
    if (!transformer.forward(bb))
        std::clog << "proj forward failed!\n";
        
    std::clog << "after forward: " << bb << "\n";

}