Merge commit '43aec5ad' into merge-2.4

Conflicts:
	cmake/OpenCVConfig.cmake
	cmake/OpenCVLegacyOptions.cmake
	modules/contrib/src/retina.cpp
	modules/gpu/doc/camera_calibration_and_3d_reconstruction.rst
	modules/gpu/doc/video.rst
	modules/gpu/src/speckle_filtering.cpp
	modules/python/src2/cv2.cv.hpp
	modules/python/test/test2.py
	samples/python/watershed.py

modules/features2d/test/test_mser.cpp

@@ -205,4 +205,3 @@ void CV_MserTest::run(int)
 }
 
 TEST(Features2d_MSER, DISABLED_regression) { CV_MserTest test; test.safe_run(); }
-