CPU (non-OpenCL) CLAHE Support for CV_16UC1 Images

The CPU implementation (non-OpenCL) implementation algorithm now supports image types of any OpenCV supported integer types.  Addresses: CLAHE Lacks Support for Other Image Types (Feature #3749).
this is another quite severe performance degradation. Division is very slow operation and you perform it in the inner-most loop. And for 8u it's not needed at all. I suggest to completely revise this part, make sure that 8u version performance does not degrade