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

diff --cc CMakeLists.txt
Simple merge

diff --cc modules/core/include/opencv2/core/utility.hpp
Simple merge

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

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

diff --cc modules/core/test/test_arithm.cpp
Simple merge

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

diff --cc modules/ts/include/opencv2/ts/ts_perf.hpp
Simple merge