[plt-scheme] Proposal for s-expr tracing format

Thanks, Shriram, I did it and it works. The main advantage, parentheses 
matching is achieved.

(
 (fibi 4)
  (
  (fibi 3)
   (
   (fibi 2)
    (
    (fibi 1)
    1
    )
    (
    (fibi 0)
    1
    )
   2
   )
   (
   (fibi 1)
   1
   )
  3
  )
  (
  (fibi 2)
   (
   (fibi 1)
   1
   )
   (
   (fibi 0)
   1
   )
  2
  )
 5
 )

Kazimir Majorinc