Changed a little to work around a bug in visual studio 2005

dlib/svm/sequence_labeler.h

@@ -79,16 +79,22 @@ namespace dlib
         template <typename T>
         two_bytes has_reject_labeling_helper(int) { return two_bytes();}
 
+        template <typename T>
+        struct work_around_visual_studio_bug
+        {
+            const static unsigned long U = sizeof(has_reject_labeling_helper<T>('a'));
+        };
+
 
         // This is a template to tell you if a feature_extractor has a reject_labeling function or not.
-        template <typename T, typename U = void > 
+        template <typename T, unsigned long U = work_around_visual_studio_bug<T>::U > 
         struct has_reject_labeling 
         {
             static const bool value = false;
         };
 
         template <typename T>
-        struct has_reject_labeling <T,typename dlib::enable_if_c<sizeof(dlib::impl::has_reject_labeling_helper<T>('a')) == 1 >::type  >
+        struct has_reject_labeling <T,1>
         {
             static const bool value = true;
         };