Merge pull request #7782 from savuor:fix/ivx_types

Several fixes for OpenVX wrappers (#7782)

* Several fixes added to ivx.hpp:
* `#include <VX/vxu.h>`
* `vx_keypoint_t` support added
* type check fixed
* fixed Node::create() for >6 args in c++98
* fixed Array::copyFrom() if array is empty
* type check changed; Array::addItem methods changed