fixed compiler warnings

dlib/dnn/input.h

@@ -208,9 +208,9 @@ namespace dlib
             auto ptr = data.host();
             for (auto i = ibegin; i != iend; ++i)
             {
-                for (long r = 0; r < NR; ++r)
+                for (size_t r = 0; r < NR; ++r)
                 {
-                    for (long c = 0; c < NC; ++c)
+                    for (size_t c = 0; c < NC; ++c)
                     {
                         rgb_pixel temp = (*i)(r,c);
                         auto p = ptr++;

examples/dnn_imagenet_train_ex.cpp

@@ -132,7 +132,7 @@ struct image_info
 {
     string filename;
     string label;
-    unsigned long numeric_label;
+    long numeric_label;
 };
 
 std::vector<image_info> get_imagenet_train_listing(