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

diff --cc cmake/OpenCVDetectCXXCompiler.cmake
Simple merge

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

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

diff --cc modules/dnn/src/op_inf_engine.hpp
Simple merge

diff --cc samples/dnn/js_face_recognition.html
Simple merge