Fixed a bug in the backtracking_line_search() function pointed out by

Ping-Chang Shih.  The function ignored the max_iter parameter.

dlib/optimization/optimization_line_search.h

@@ -512,7 +512,7 @@ namespace dlib
         unsigned long iter = 0;
         while (true)
         {
-            ++max_iter;
+            ++iter;
             const double val = f(alpha);
             if (val <= f0 + alpha*rho*d0 || iter >= max_iter)
             {