Doxygen tutorials: warnings cleared

doc/tutorials/features2d/feature_detection/feature_detection.markdown

@@ -7,7 +7,7 @@ Goal
 In this tutorial you will learn how to:
 
 -   Use the @ref cv::FeatureDetector interface in order to find interest points. Specifically:
-    -   Use the @ref cv::SurfFeatureDetector and its function @ref cv::detect to perform the
+    -   Use the @ref cv::xfeatures2d::SURF and its function @ref cv::xfeatures2d::SURF::detect to perform the
         detection process
     -   Use the function @ref cv::drawKeypoints to draw the detected keypoints
 
@@ -72,6 +72,7 @@ int main( int argc, char** argv )
   void readme()
   { std::cout << " Usage: ./SURF_detector <img1> <img2>" << std::endl; }
 @endcode
+
 Explanation
 -----------
 
@@ -85,5 +86,3 @@ Result
 2.  And here is the result for the second image:
 
     ![image](images/Feature_Detection_Result_b.jpg)
-
-