Succes! I got my version of cl-sdl running using the generated UFFI bindings for gl.lisp instead of the original ones. I tried some of the demoes, and things seem to be fine.
Allowing for overrides took about half an hour of work. I then spent another half hour fixing some other problems relating to names of parameters. But that was basically it.
Next up, I'll take a look at using the generator for glu.lisp as well. But that won't be for today. I have some peasant magic planned this afternoon. :-)