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

diff --cc doc/Doxyfile.in
Simple merge

diff --cc doc/tutorials/calib3d/real_time_pose/real_time_pose.markdown
Simple merge

diff --cc modules/calib3d/include/opencv2/calib3d.hpp
Simple merge

diff --cc modules/core/include/opencv2/core/cvdef.h
Simple merge

diff --cc modules/core/src/system.cpp
Simple merge

diff --cc modules/dnn/CMakeLists.txt
Simple merge

diff --cc modules/dnn/src/ie_ngraph.cpp
Simple merge

diff --cc modules/dnn/src/layers/crop_and_resize_layer.cpp
Simple merge

diff --cc modules/imgproc/src/contours.cpp
Simple merge

diff --cc modules/imgproc/src/templmatch.cpp
Simple merge

diff --cc modules/imgproc/test/test_contours.cpp
Simple merge

diff --cc modules/imgproc/test/test_templmatch.cpp
Simple merge

diff --cc modules/stitching/src/matchers.cpp
Simple merge