Matteo Bruni (@Mystral) commented about include/d3dx9tex.h:
D3DFORMAT srcformat, UINT srcrowpitch, UINT srcslicepitch, const PALETTEENTRY *srcpalette, const D3DBOX *srcbox, DWORD filter, D3DCOLOR colorkey);
+HRESULT WINAPI D3DXSaveVolumeToFileInMemory(struct ID3DXBuffer **destbuffer, D3DXIMAGE_FILEFORMAT destformat,
struct IDirect3DVolume9 *srcvolume, const PALETTEENTRY *srcpalette, const D3DBOX *srcbox);
This would need to go with the test, if you follow my suggestion above. Or, it could also be a separate patch at the start of the series.