Merge pull request #4098 from asmorkalov:as/cuda_warn_fix

Fixed build warnings in CUDA.

Author: asmorkalov

modules/cudacodec/include/opencv2/cudacodec.hpp

@@ -395,6 +395,7 @@ class CV_EXPORTS_W NVSurfaceToColorConverter {
      * @param stream Stream for the asynchronous version.
      */
     CV_WRAP virtual bool convert(InputArray yuv, OutputArray color, const SurfaceFormat surfaceFormat, const ColorFormat outputFormat, const BitDepth bitDepth = BitDepth::UNCHANGED, const bool planar = false, cuda::Stream& stream = cuda::Stream::Null()) = 0;
+    virtual ~NVSurfaceToColorConverter() {};
 };
 
 /** @brief Creates a NVSurfaceToColorConverter.

modules/cudafeatures2d/include/opencv2/cudafeatures2d.hpp

@@ -118,11 +118,11 @@ class CV_EXPORTS_W DescriptorMatcher : public cv::Algorithm
 
     /** @brief Clears the train descriptor collection.
      */
-    CV_WRAP virtual void clear() = 0;
+    CV_WRAP virtual void clear() CV_OVERRIDE = 0;
 
     /** @brief Returns true if there are no train descriptors in the collection.
      */
-    CV_WRAP virtual bool empty() const = 0;
+    CV_WRAP virtual bool empty() const CV_OVERRIDE = 0;
 
     /** @brief Trains a descriptor matcher.