Changed code to avoid compiler warning.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403109

examples/surf_ex.cpp

@@ -70,7 +70,7 @@ int main(int argc, char** argv)
         {
             // Pull out the info from the SURF point relevant to figuring out
             // where its rotated box should be.
-            const double box_size = sp[i].p.scale*10;
+            const unsigned long box_size = static_cast<unsigned long>(sp[i].p.scale*10);
             const double ang = sp[i].angle;
             const point center(sp[i].p.center);
             rectangle rect = centered_rect(center, box_size, box_size);