Merge remote-tracking branch 'upstream/3.4' into merge-3.4

doc/tutorials/features2d/table_of_content_features2d.markdown

@@ -89,6 +89,8 @@ OpenCV.
 
 -   @subpage tutorial_detection_of_planar_objects
 
+    *Languages:* C++
+
     *Compatibility:* \> OpenCV 2.0
 
     *Author:* Victor Eruhimov
@@ -108,6 +110,8 @@ OpenCV.
 
 -   @subpage tutorial_akaze_tracking
 
+    *Languages:* C++
+
     *Compatibility:* \> OpenCV 3.0
 
     *Author:* Fedor Morozov
@@ -116,6 +120,8 @@ OpenCV.
 
 -   @subpage tutorial_homography
 
+    *Languages:* C++, Java, Python
+
     *Compatibility:* \> OpenCV 3.0
 
     This tutorial will explain the basic concepts of the homography with some