core: prevent changes in 'std' namespace

modules/core/include/opencv2/core/cvstd.hpp

@@ -67,6 +67,11 @@
 
 namespace cv
 {
+    static inline uchar abs(uchar a) { return a; }
+    static inline ushort abs(ushort a) { return a; }
+    static inline unsigned abs(unsigned a) { return a; }
+    static inline uint64 abs(uint64 a) { return a; }
+
     using std::min;
     using std::max;
     using std::abs;
@@ -77,14 +82,6 @@ namespace cv
     using std::log;
 }
 
-namespace std
-{
-    static inline uchar abs(uchar a) { return a; }
-    static inline ushort abs(ushort a) { return a; }
-    static inline unsigned abs(unsigned a) { return a; }
-    static inline uint64 abs(uint64 a) { return a; }
-}
-
 #else
 namespace cv
 {