Optimize OpenCL version of BFMatcher
BackgroundSubtractorMOG2, learningRate=0 optimization
Merge pull request #3256 from vbystricky:oclopt_BFMatcher
Changed predictOptimalVectorWidth function, now it is possible to choose vector size.
Merge pull request #3355 from ElenaGvozdeva:predictOptimalVectorWidth
Merge pull request #3352 from alucarded:BackgroundSubtractorMOG2_optimization