added 3-channel support to arithmetic operations
3-channel support in OpenCL kernels for setTo, resize, warpAffine and warpPerspective
fixed OpenCL kernel flag in resize (thanks to Ilya L)
Deleted an assignment to a variable that doesn't exist.
Merge pull request #2326 from vpisarev:ocl_ch3
Merge pull request #2336 from SpecLad:useOclChanged
UMat: issue in OpenCLAllocator::unmap()