Restore OpenCL branch for minmaxLoc on float data
moved nonfree and a part of features2d to opencv_contrib/xfeatures2d
fixed doc builder complains and the test failures
removed the stuff that's now in xfeatures2d; temporarily added dummy definition of SIFT to make doc builder pass (will remove it later)
removed the stuff that's now in xfeatures2d; temporarily added dummy definition of SIFT to make doc builder pass (will remove it later)
CPU (non-OpenCL) CLAHE now supports CV_16UC1.
fixed more doc builder warnings
Remove mul24, for CV8UC3 3840x2160 it generates implementation specific result
fixed Erode and Dilate in case of kernel = Mat()
Merge pull request #3073 from vbystricky:ocl_fixMinMaxLoc
removed some more trailing whitespaces
Merge pull request #3033 from nathanjackson:clahe_datatypes
fixed test for ocl PlaneWarperTest
Merge pull request #3078 from vpisarev:refactor_features2d_take3
Merge pull request #3082 from ElenaGvozdeva:ocl_morphSmall
Merge pull request #3080 from ElenaGvozdeva:ocl_stich