windows.media: Implement IActivationFactory::ActivateInstance() for IMediaTranscoder.
Needed by LINE.
The IMediaTranscoder2 definition isn't needed for this, but it's small enough to add in case it's used by mingw.
Needed by LINE.
The IMediaTranscoder2 definition isn't needed for this, but it's small enough to add in case it's used by mingw.