[patch, fortran] Fix PR 32977

[FX Coudert]

> 2007-07-29  Thomas Koenig  <tkoenig@gcc.gnu.org>
>
> 	PR libfortran/32977
> 	* io/unix.c:  If there is no vsnprintf, use vsprintf and issue
> 	a fatal error when a buffer overrun occurs.

OK