parallel cvtColor for MSVS and Apple

modules/imgproc/src/color.cpp

@@ -192,8 +192,11 @@ void CvtColorLoop(const Mat& src, Mat& dst, const Cvt& cvt)
 {
     Range range(0, src.rows);
     CvtColorLoop_Invoker<Cvt> invoker(src, dst, cvt);
+#if defined(_MSC_VER) || defined(__APPLE__)
+    parallel_for_(range, invoker);
+#else
     invoker(range);
-//     parallel_for_(range, invoker);
+#endif
 }
 
 ////////////////// Various 3/4-channel to 3/4-channel RGB transformations /////////////////