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

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

diff --cc modules/highgui/src/window_gtk.cpp
Simple merge

diff --cc modules/imgcodecs/src/grfmt_exr.cpp
Simple merge

diff --cc modules/objdetect/src/hog.cpp
Simple merge