Merge with master and fix conflicts

samples/cpp/tutorial_code/HighGUI/AddingImagesTrackbar.cpp

@@ -4,6 +4,7 @@
  * @author OpenCV team
  */
 
+#include "opencv2/imgcodecs.hpp"
 #include "opencv2/highgui/highgui.hpp"
 #include <stdio.h>
 

samples/cpp/tutorial_code/HighGUI/BasicLinearTransformsTrackbar.cpp

@@ -5,6 +5,7 @@
  * @author OpenCV team
  */
 
+#include "opencv2/imgcodecs.hpp"
 #include "opencv2/highgui/highgui.hpp"
 
 using namespace cv;

samples/cpp/tutorial_code/HighGUI/video-input-psnr-ssim/video-input-psnr-ssim.cpp

@@ -5,6 +5,7 @@
 
 #include <opencv2/core/core.hpp>        // Basic OpenCV structures (cv::Mat, Scalar)
 #include <opencv2/imgproc/imgproc.hpp>  // Gaussian Blur
+#include <opencv2/videoio/videoio.hpp>
 #include <opencv2/highgui/highgui.hpp>  // OpenCV window I/O
 
 using namespace std;

samples/cpp/tutorial_code/HighGUI/video-write/video-write.cpp

@@ -2,7 +2,7 @@
 #include <string>   // for strings
 
 #include <opencv2/core/core.hpp>        // Basic OpenCV structures (cv::Mat)
-#include <opencv2/highgui/highgui.hpp>  // Video write
+#include <opencv2/videoio/videoio.hpp>  // Video write
 
 using namespace std;
 using namespace cv;