finished with NV12 support for D3D11-interop. Now, if texture is in NV12 format then it will be converted to/from BGR UMat.

fixed issues with ocl nv12 cvt kernel

finisged ocl nv12-to-rgba kernel, update dx-interop samples. (ocl rgba-to-nv12 kernel will be added later)

an attempt to fix build issue

fix for non opencl build issue

fix typo

fix compilation warnings

fix compile issue for Mac (OpenCL)

add convertion from rgba to nv12 (still need to debug kernel)

remove empty line at the EOF

fixed compilation warning

Signed-off-by: NYan Wang <yan.wang@linux.intel.com>

rewrite & change convertFromGLBuffer() & convertToGLBuffer() into acquireGLBuffer() & releaseGLBuffer(), respectively

opengl sample: added buffer support

tested and fixed buffer support on Windows

change glFlush() call to glFinish()

added UMat::release() call; fixed functions' names

adopted & implemented API suggestion(s) from Alexander

fixed unreachable code warning

added more info to the mapGLBuffer/unmapGLBuffer description

http://code.opencv.org/issues/4462

Fixed errors in parallel_for based on pthreads

Fixing compiler errore & removing whitespaces

Fixing prallel_for_pthreads error and warnings on win

057cd52 first versions: cv::ogl::convertFromGLTexture2D & cv::ogl::convertToGLTexture2D
5656e94 added autogenerated stuff for cl_gl.h
765f1fd resolved CL functions in opengl.cpp
9f9fee3 implemented function cv::ogl::ocl::initializeContextFromGLTexture2D()
a792adb cv::ogl::ocl::initializeContextFromGLTexture2D() - added linux support (glx.h)
51c2869 added missing error message in function cv::ogl::ocl::initializeContextFromGLTexture2D()
513b887 fixed extension call in function cv::ogl::ocl::initializeContextFromGLTexture2D()
475a3e9 added CL-GL interop Windows sample (gpu/opengl_interop.cpp)
07af28f added building of CL-GL interop sample - Windows only
befe3a2 fixed whitespace errors & doxygen warnings (precommit_docs)
551251a changed function name to cv::ogl::ocl::initializeContextFromGL(), removed unused argument
4d5f009 changed CL_DEVICES_FOR_GL_CONTEXT_KHR to CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KHR
9fc3055 changed CL_DEVICES_FOR_GL_CONTEXT_KHR to CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KH
6d31cee Revert "changed CL_DEVICES_FOR_GL_CONTEXT_KHR to CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KH"
cc6a025 added texture format check in cv::ogl::convertFromGLTexture2D()
063a2c1 CL-GL sample: added Linux implementation (Xlib/GLX)
c392ae9 fixed trailing whitespace
85a80d0 fixed include files
ae23628 excluded samples/opengl from build case 2
9870ea5 added android EGL support
530b64c added doxygen documentation comments to CL-GL interop functions

Some code style corrections;

Commits:
added new function, cv::ocl::attachContext(String& platformName, void* platformID, void* context, void* deviceID) which allow to attach externally created OpenCL context to OpenCV.
add definitions of clRetainDevice, clRetainContext funcs
removed definitions for clRetainContext, clRetainDevice
fixed build issue under Linux
fixed uninitialized vars, replace dbgassert in error handling
remove function which is not ready yet
add new function, cv::ocl::convertFromBuffer(int rows, int cols, int type, void* cl_mem_obj, UMat& dst, UMatUsageFlags usageFlags = cv::USAGE_DEFAULT) which attaches user allocated OpenCL clBuffer to UMat
uncommented clGetMemObjectInfo definition (otherwise prevent opencv build)
fixed build issue on linux and android
add step parameter to cv::ocl::convertFromBuffer func
suppress compile-time warning
added sample opencl-opencv interoperability (showcase for cv::ocl::convertFromBuffer func)
CMakeLists.txt modified to not create sample build script if OpenCL SDK not found in system
fixed build issue (apple opencl include dir and spaces in CMake file)
added call to clRetainContext for attachContext func and call to clRetainMemObject for convertFromBuffer func
uncommented clRetainMemObject definition
added comments and cleanup
add local path to cmake modules search dirs (instead of replacing)
remove REQUIRED for find_package call (sample build together with opencv). need to try standalone sample build
opencl-interop sample moved to standalone build
set minimum version requirement for sample's cmake to 3.1
put cmake_minimum_required under condition, so do not check if samples not builded
remove code dups for setSize, updateContinuityFlag, and finalizeHdr
commented out cmake_minimum_required(VERSION 3.1)
add safety check for cmake version
add convertFromImage func and update opencl-interop sample
uncommented clGetImageInfo defs
uncommented clEnqueueCopyImageToBuffer defs
fixed clEnqueueCopyImageToBuffer defs
add doxygen comments
remove doxygen @fn tag
try to restart buildbot
add doxygen comments to directx interop funcs
remove internal header, use fwd declarations in affected compile units instead

Removed IPP port for tiny arithm.cpp functions

Additional warnings fix on various platforms.

Build without OPENCL and GCC warnings fixed

Fixed warnings, trailing spaces and removed unused secure_cpy.

IPP code refactored.

IPP code path  implemented as separate static functions to simplify future work with IPP code and make it more readable.

made improvements in ECC code (comments from https://github.com/Itseez/opencv/pull/3845), as well as minor tweak in pthread's based parallel for.

removing trailing whitespaces

Compilation error on Mac fix & warning on android

Warnings fixed on iOs

hack solvePoly to finds roots of polynoms with zero higher-order coefficients. The roots are populated in this case, which is not valid, strictly speaking, but good enough for function like correctMatches. This solves http://code.opencv.org/issues/4330

fix MatOpInitializer

removed HAL calls from public OpenCV headers; put IPP calls back to hall:sqrt() and such (but they are disabled for now)

http://code.opencv.org/issues/2206,
http://code.opencv.org/issues/2924

use _mm_sad_epu8 instead of _mm_movemask_epi8 in countNonZero. Therefore, we do not need any popcount table and this solves http://code.opencv.org/issues/4333