Re: [PATCH v4 0/3] MR2727: hrtfapo: Add CreateHrtfApo() stub.

[Rémi Bernon (＠rbernon)]

```suggestion:-12+0
HRESULT __stdcall CreateHrtfApo([in] const HrtfApoInit *init, [out] IXAPO **xapo);

[
    object,
    uuid(15b3cd66-e9de-4464-b6e6-2bc3cf63d455)
]
interface IXAPOHrtfParameters : IUnknown
{
    HRESULT SetSourcePosition([in] const HrtfPosition *position);
    HRESULT SetSourceOrientation([in] const HrtfOrientation *orientation);
    HRESULT SetSourceGain([in] float gain);
    HRESULT SetEnvironment([in] HrtfEnvironment environment);
}
```

I don't really know how much this matters, but the SDK header has `_In_` / `_COM_Outptr_`. There's no public IDL to compare to, but I think we could add the attributes there as well.

Note that you only really need the `CreateHrtfApo` function for your stub, so this is a bit superfluous (though alright given that the header is small).