Merge remote-tracking branch 'origin/2.4' into merge-2.4

Conflicts:
	modules/core/include/opencv2/core/operations.hpp
	modules/core/include/opencv2/core/version.hpp
	modules/core/src/gpumat.cpp
	modules/cudaimgproc/src/color.cpp
	modules/features2d/src/orb.cpp
	modules/imgproc/src/samplers.cpp
	modules/ocl/include/opencv2/ocl/matrix_operations.hpp
	modules/ocl/include/opencv2/ocl/ocl.hpp
	samples/ocl/facedetect.cpp