[racket] Integrating scribble and LaTeX

Thanks Matthew.

> Otherwise, to just typeset Racket code, you might want to use
> `slideshow/pict' and `slideshow/code', instead.

Indeed, it works quite nicely. I was surprised not to find a pict->pdf function, but that was not too hard to write.

> (It would be nice if those were more unified.... one day.)

Indeed! 
Things I will miss from Scribble are code:hilite, and the interactions. 
But I can live with that meanwhile.

-- Éric