[patch] fix PR libfortran/20179

[Tobias Schlüter]

FX Coudert wrote:
> 2005-09-11  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
> 
> 	PR libfortran/20179
> 	* io/unix.c (is_preconnected): Add function to test if a stream
> 	corresponds to a preconnected unit.
> 	* io/io.h: Add prototype for is_preconnected.
> 	* io/transfer.c (data_transfer_init): Do not truncate
> 	preconnected units.

OK.  I don't think 4.0 is frozen yet, so it's ok there as well.

- Tobi