games/xray_re-tools: unbreak the build against new nVidia Texture Tools

In 2020 Ignacio had modified the API with NVTT upstream commit adce1a00
which must have been cleanup, but was more than that. Particularly, it
shuffled things around DirectDrawSurface class, and thus had broken the
port's build. While here, remove all bundled 3rd-party code to prevent
accidental use thereof.