[1/5] windowscodecs: Implement IWICStream::InitializeFromIStream.

[Vincent Povirk]

> +static HRESULT WINAPI StreamOnStream_Seek(IStream *iface,
> +    LARGE_INTEGER dlibMove, DWORD dwOrigin, ULARGE_INTEGER *plibNewPosition)
> +{
> +    StreamOnStream *This = StreamOnStream_from_IStream(iface);
> +    HRESULT hr=S_OK;
> +    TRACE("(%p)\n", This);
> +
> +    EnterCriticalSection(&This->lock);
> +    hr = IStream_Seek(This->stream, dlibMove, dwOrigin, plibNewPosition);
> +    LeaveCriticalSection(&This->lock);
> +
> +    return hr;
> +}

The IWICStream needs to have an independent position from the underlying stream.

Also, why not just forward to InitializeFromIStreamRegion?