[racket] Racket doesn't prompt to debug open .SS files

Apologies if this is already bugged (or considered a non-bug), but:

Using Racket on an old PLT Scheme 4 project with .SS files. Debugger
didn't prompt offering to debug other open .SS files used by the main
file.

After a couple minutes of "huh"-ing and "frak"-ing I took a guess and
renamed all the files from SS to RKT. Now it works.

Not a big deal if you plan to rename anyway (as I planned to) but
wanted to mention it in case the intent was for this feature to
continue to work with old .SS files.

If I should go bug this up let me know.

Cheers,
Greg