direct3d11: add AMD HQ Scaler upscaler
And fix initial render position when using the upscaler.
Also cleanup the detection of D3D11/D3D9 headers which are always there given the mingw-w64 version we require.
The AMD HQ Scaler is an interface-only API. The system DLL has to be loaded manually. After that we can query what we need, just as a COM interface. More info: https://github.com/GPUOpen-LibrariesAndSDKs/AMF/blob/master/amf/doc/AMF_HQ_Scaler_API.md