work around bug in visual studio

dlib/test/global_optimization.cpp

@@ -234,7 +234,7 @@ namespace
         print_spinner();
 
         constexpr auto close_enough = -16.0;
-        auto early_result = find_max_global([&early_evals](double x){ early_evals++; return -std::pow(x-2,2.0); }, -10, 1, max_function_calls(10), 0.0, std::vector<function_evaluation>{}, [](double y){ return (y >= close_enough);});
+        auto early_result = find_max_global([&early_evals](double x){ early_evals++; return -std::pow(x-2,2.0); }, -10, 1, max_function_calls(10), 0.0, std::vector<function_evaluation>{}, [&](double y){ return (y >= close_enough);});
         dlog << LINFO << "(x-2)^2, bound at 1: " <<  trans(early_result.x);
         DLIB_TEST(early_result.x.size()==1);
         DLIB_TEST(std::abs(early_result.y) <= std::abs(close_enough));