Updated DisplayImage.cpp program to compile

CV_WINDOW_AUTOSIZE -> WINDOW_AUTOSIZE

doc/tutorials/introduction/linux_gcc_cmake/linux_gcc_cmake.rst

@@ -41,7 +41,7 @@ Let's use a simple program such as DisplayImage.cpp shown below.
          return -1;
        }
 
-     namedWindow( "Display Image", CV_WINDOW_AUTOSIZE );
+     namedWindow( "Display Image", WINDOW_AUTOSIZE );
      imshow( "Display Image", image );
 
      waitKey(0);