- fixed uninitialized memory access and memory leaks
- extracted several code blocks to separate functions
- updated part of algorithm to use cv::Mat instead of CvMat and IplImage

* bypass makro

* syntax

1) Cameras started with Y16 (V4L2_PIX_FMT_Y16) format via v4l2 backend will now exhibit default camera behavior, i.e. convert the 16-bit image to BGR as with all other formats. 16-bit 1-channel output will now only be produced for Y16 if CV_CAP_PROP_CONVERT_RGB is set to "false" using VideoCap::set method.
2) v4l2 videoio backend now supports setting CV_CAP_PROP_FOURCC explicitly (icvSetPropertyCAM_V4L function in cap_v4l.cpp), allowing users to manually set the codec on cameras that support multiple codecs.

  * __fp16 doesn't exist on nvcc, but it slips through ifdef guard

Fixes clang -Wextra-semi warnings.