build: fix build with GCC 4.8

modules/dnn_superres/samples/dnn_superres_multioutput.cpp

@@ -31,20 +31,25 @@ int main(int argc, char *argv[])
     std::string path = string(argv[4]);
 
     //Parse the scaling factors
-    std::stringstream ss(scales_str);
     std::vector<int> scales;
-    std::string token;
     char delim = ',';
+    {
+        std::stringstream ss(scales_str);
+        std::string token;
         while (std::getline(ss, token, delim)) {
             scales.push_back(atoi(token.c_str()));
         }
+    }
 
     //Parse the output node names
-    ss = std::stringstream(output_names_str);
     std::vector<String> node_names;
+    {
+        std::stringstream ss(output_names_str);
+        std::string token;
         while (std::getline(ss, token, delim)) {
             node_names.push_back(token);
         }
+    }
 
     // Load the image
     Mat img = cv::imread(img_path);