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

Conflicts:
	CMakeLists.txt
	cmake/OpenCVDetectCUDA.cmake
	doc/tutorials/features2d/feature_flann_matcher/feature_flann_matcher.rst
	modules/core/src/cmdparser.cpp
	modules/gpu/CMakeLists.txt
	modules/gpu/doc/introduction.rst
	modules/gpu/perf/perf_video.cpp
	modules/highgui/doc/reading_and_writing_images_and_video.rst
	modules/ocl/src/cl_context.cpp
	modules/video/include/opencv2/video/background_segm.hpp
	samples/cpp/image_sequence.cpp
	samples/cpp/tutorial_code/ImgTrans/HoughCircle_Demo.cpp
	samples/python/chessboard.py
	samples/python/cvutils.py
	samples/python/demhist.py
	samples/python/dft.py
	samples/python/distrans.py
	samples/python/edge.py
	samples/python/ffilldemo.py
	samples/python/fitellipse.py
	samples/python/houghlines.py
	samples/python/inpaint.py
	samples/python/logpolar.py
	samples/python/morphology.py
	samples/python/numpy_array.py
	samples/python/watershed.py