fixed perf test
corners
Openni2 support
Merge remote-tracking branch 'origin/master' into Openni2Support

Conflicts:
	modules/highgui/CMakeLists.txt
	modules/highgui/include/opencv2/highgui.hpp
	modules/highgui/include/opencv2/highgui/highgui_c.h
Openni2 support
Fix build errors with cap_v4l on Linux
Merge pull request #2986 from vbystricky:videoio_fix
Merge pull request #2960 from ilya-lavrenov:tapi_perf_fix
Add depends from highgui to imgcodecs and videoio. And include header from imgcodecs and videoio to imgcodecs
Merge pull request #2961 from ilya-lavrenov:tapi_corners
Fixed ippiDFT call
Merge pull request #2995 from ElenaGvozdeva:ipp_DFT
Merge pull request #2919 from larshg:Openni2Support
Merge pull request #2990 from vbystricky:highgui_split2
Initialize all pointers of CvCapture_GStreamer correctly
Reset class members to NULL after gst_*_unref()