core dump closing output port interactively

[Marco Maggi]

With Guile 1.8.1 but works with .0 too:

$ guile
> (close (current-error-port))
#t
> (close (current-input-port))
#t

-> segmentation fault

The stack trace shows a lot of recursive calls to
scm_gc_mark and scm_gc_mark_dependencies with the fault
happening at line 303 of gc-mark.c.

$ guile
> (close (current-error-port))
#t
> (close (current-output-port))

-> segmentation fault

The same stack trace.