[plt-scheme] reindent code

If, by chance, you just want a quick&dirty command-line reindenter 
program for internal use, you might be able to get by with making a 
shell script wrapper around Emacs in batch mode.

You'd have Emacs require Quack, open the file, execute "quack-tidy", 
write the file, and exit.

If you disable Emacs loading of site and user configs, you should be 
able to get total wall clock run time for the program in the 
neighborhood of 1-3 seconds on an ordinary PC, especially on repeated 
invocations while Emacs text is in caches.

Emacs with Quack indents almost identically to DrScheme.  Beware that 
"quack-tidy" doesn't know about PLT's here-document syntax, and will 
mess that up badly.