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)

See pull request #1241 for why.

do not calculate sum of error in every round of iteration;
instead the error will be summed every 2nd times or more, 
if the previous sum of error is too far away from threshold.