OCL: Optimize OpenCL version of StereoBM function

1. Fix problems on NVidia devices.
2. Move some arguments to build options
3. Refactoring some code.

http://ocl.itseez.com/intel/export/perf/pr/3284/report/

check_regression=*OCL*StereoBM*
test_filter=*OCL*StereoBM*
test_modules=calib3d
build_examples=OFF
Sorry may be i don't undestand this idea. 
Now we sum i-th column to the `costbuf[i]`, i can change definition of the `costbuf` to `short4 costbuf[(WSZ + 3) / 4]` (4 is for example) and sum them. Then i need to acces to the `i-th` element, if i use `short` i can do this by `costbuf[i]`, if i use vectors how can i do this?
And another small problem: `WSZ` is arbitrary and isn't divisible to `4` or `8`. Thus if i will use a vectors in a sum i need additional code for work with tails.