[racket] Changing at-expressions to other-glyph-expressions

> "But you can move the defines outside the @list| form, as seen in
> https://gist.github.com/dyoo/5423623." True, but in that case, I can no
> longer programmatically parse my source files, since they may have defines
> within them. (This is, as I understand it, the major benefit of using
> scribble/text as a preprocessor — you get all the Racket constructs. Define
> is a big one ;)

Oh!  Ok, here's a quick and dirty hack I did to make that work:

    https://gist.github.com/dyoo/5424171

I just cooked this up from copy-and-pasting the content of
racket/block and hacking it to do something appropriate for Scribble,
so it might be a bit fragile.  I have not tested it heavily yet.