DSOAL r554 - Add a Buffer::SetFX stub

DSOAL r554@4be16f9e c++-rewrite - Add a Buffer::SetFX stub [2024-09-05 03:02:49 +0000]
OpenAL Soft r9342@a4e126ac master - Don't assert for unexpected FX slot IDs [2024-09-02 15:40:24 +0000]
Build log: https://github.com/ThreeDeeJay/dsoal/actions/runs/10752448542/job/29820782853

Full Changelog: r503...r554