printing structures

[attardi%dipisa.DI.UNIPI.IT@CUNYVM.CUNY.EDU]

When printing a structure which has its own print-function, extra indentation
is produced.

Example:

> (defstruct (foo (:print-structure (lambda (x s d) (princ "FOO")))))
FOO
> (list 1 (make-foo))
(1
 FOO)
>