added epsilon value to weights in the MergeMertens in order to avoid zero weights for pixels from uniformly filled areas of image
added test for correct handling of uniforma areas in the MergeMertens
Merge remote-tracking branch 'origin/2.4' into merge-2.4

Conflicts:
	cmake/OpenCVDetectAndroidSDK.cmake
	cmake/OpenCVGenAndroidMK.cmake
	cmake/OpenCVModule.cmake
	cmake/templates/OpenCV.mk.in
	cmake/templates/OpenCVConfig.cmake.in
	doc/tutorials/imgproc/histograms/histogram_comparison/histogram_comparison.rst
	modules/cudabgsegm/src/cuda/mog.cu
	modules/imgproc/perf/opencl/perf_filters.cpp
	modules/imgproc/src/opencl/filterSep_singlePass.cl
	modules/nonfree/CMakeLists.txt
	modules/nonfree/perf/perf_precomp.hpp
	modules/ocl/perf/perf_haar.cpp
	modules/ocl/src/filtering.cpp
	modules/ocl/src/opencl/bgfg_mog.cl
	modules/superres/CMakeLists.txt
	modules/superres/src/btv_l1_cuda.cpp
	modules/superres/src/cuda/btv_l1_gpu.cu
	modules/superres/src/frame_source.cpp
	modules/superres/src/input_array_utility.cpp
	modules/superres/src/optical_flow.cpp
	modules/superres/src/precomp.hpp
	samples/gpu/CMakeLists.txt
	samples/gpu/brox_optical_flow.cpp
	samples/gpu/super_resolution.cpp
ocl morphology fix
Merge pull request #2524 from SpecLad:merge-2.4
Merge pull request #2526 from KonstantinMatskevich:ocl_morph_fix
Merge pull request #2123 from white-pony:vkysenko/fix-mertens
Merge pull request #2523 from ilya-lavrenov:tapi_filters
improved cv::filter2D