- Before this PR, following tests failed on some platform.
  CUDA_OptFlow/FarnebackOpticalFlow.Accuracy/19
  CUDA_OptFlow/FarnebackOpticalFlow.Accuracy/23

- The algorithm now recognizes the OPTFLOW_USE_INITIAL_FLOW flag.
  Previously, when the flag was set, it did not use the flow data
  passed as input, instead used some garbage data in memory.

- More strict test limit.

upload winsize and iters as members to prevent async out of scope issues

cpmpatability

texture channels were not considered correctly, nor was the cuda texture
normalization

Modified sparse pyrlk optical flow to allow input of an image pyramid which thus allows caching of image pyramids on successive calls.
Added unsigned char support for 1, 3, 4 channel images.

* use opaque algorithm interfaces
* add stream support

it caused runtime failures

* it is the only place, where it is used
* no need to make this function public

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