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/core/perf/perf_abs.cpp

@@ -24,4 +24,3 @@ PERF_TEST_P(Size_MatType, abs, TYPICAL_MATS_ABS)
 
     SANITY_CHECK(c);
 }
-

modules/core/perf/perf_bitwise.cpp

@@ -73,4 +73,3 @@ PERF_TEST_P(Size_MatType, bitwise_xor, TYPICAL_MATS_BITW_ARITHM)
 
     SANITY_CHECK(c);
 }
-

modules/core/perf/perf_merge.cpp

@@ -34,4 +34,4 @@ PERF_TEST_P( Size_SrcDepth_DstChannels, merge,
     TEST_CYCLE_MULTIRUN(runs) merge( (vector<Mat> &)mv, dst );
 
     SANITY_CHECK(dst, 1e-12);
-}
+}