2. fixed parsing of "cat[range_spec]ord[range_spec]" type specification string when using ml::TrainData::loadFromCSV(). Thanks to A. Kaehler for reporting it

  * raise an error when wrong bit depth passed
  * raise an build error when wrong depth is specified for cvtScaleHalf_
  * remove unnecessary safe check in cvtScaleHalf_
  * use intrinsic instead of direct pointer access
  * update the explanation

Cast to (int) to avoid warnings

Add test for different points number case in fisheye calibration function

  * add feature of Fp16 on GPU (cudev)
  * add test
  * leave template function as unimplemented to raise error

  * make sure that CV_FP16 has the correct meaning
  * check FP16 feature correctly

amends work done in pull request #6976.