T-API: used built-in functions in core module

**Performance report:**
http://ocl.itseez.com/intel/export/perf/pr/2852/report/

check_regression=*OCL*Norm*:*OCL*MinMaxL*:*OCL*Add*:*OCL*Log*:*OCL*Abs*:*OCL*Patch*:*OCL*Polar*:*OCL*Scale*:*OCL*Sum*
test_filter=*OCL*Norm*:*OCL*MinMaxL*:*OCL*Add*:*OCL*Log*:*OCL*Abs*:*OCL*Patch*:*OCL*Polar*:*OCL*Scale*:*OCL*Sum*
test_modules=core
build_examples=OFF
Try something like this:
```
(oclop == OCL_OP_ABSDIFF && wdepth == CV_32S && ddepth == wdepth)
    ? ocl::convertTypeStr(CV_8U, CV_32S, kercn, cvtstr[2]) // CV_8U is a hack for non-existed CV_32U
    : ocl::convertTypeStr(wdepth, ddepth, kercn, cvtstr[2]),
```