Merged requested to merge seungha.yang/gst-plugins-bad:d3d11-code-cleanup into master
- Remove unnecessary upcasting. We are now dealing with C++ class objects and don't need explicit C-style casting in C++ world
- Use helper macro IID_PPV_ARGS() everywhere. It will make code a little short.
- Use ComPtr smart pointer instead of calling manual IUnknown::Release()