Removed unneeded declarations of the constant pi

dlib/image_keypoint/fine_hog_image.h

@@ -240,7 +240,6 @@ namespace dlib
             hist_counts.set_size(img.nr()-2, img.nc()-2);
 
 
-            const double pi = 3.1415926535898;
 
 
             for (long r = 0; r < hist_counts.nr(); ++r)

dlib/image_keypoint/hog.h

@@ -282,7 +282,6 @@ namespace dlib
                 }
             }
 
-            const double pi = 3.1415926535898;
 
             // loop over all the histogram cells and fill them out
             for (long rh = 1; rh < hist_cells.nr()-1; ++rh)

dlib/image_keypoint/surf.h

@@ -88,7 +88,6 @@ namespace dlib
             << "\n\t scale:         " << scale 
         );
 
-        const double pi = 3.1415926535898;
 
         std::vector<double> ang;
         std::vector<dlib::vector<double,2> > samples;

dlib/test/geometry.cpp

@@ -273,7 +273,6 @@ namespace
         }
 
         {
-            const double pi = 3.1415926535898;
             point p1, center;
 
             center = point(3,4);