Consider this a part of merging #1357.

Conflicts:
	modules/contrib/src/retina.cpp
	modules/gpu/perf/perf_video.cpp
	modules/gpuoptflow/src/tvl1flow.cpp
	modules/ocl/include/opencv2/ocl/ocl.hpp
	modules/ocl/perf/perf_calib3d.cpp
	modules/ocl/perf/perf_color.cpp
	modules/ocl/perf/perf_match_template.cpp
	modules/ocl/src/precomp.hpp
	samples/gpu/stereo_multi.cpp

libpng 1.5+ recommends a call to png_set_interlace_handling() if you use
png_read_update_info and png_read_image. It will generate a warning
without it.

Also removed malformed tEXt chunk from a logo PNG.

Some changes in OpenCV

enabled some tests that failed before OCL_TEST_CYCLE*() macroses were defined and for some tests was disabled SANITY_CHECK, because plain and ocl results must not be completely equal

fixed building OpenCV with IPP 6.x (different DFT API); added Canny and rectangular morphology (based on Alex Kapustin patches)