[m-rev.] for review: add system_error_is_success/1

[Peter Wang]

On Sun, 12 Feb 2023 20:48:49 +1100 Julien Fischer <jfischer at opturion.com> wrote:
> 
> For review by anyone.
> 
> ----------------------
> 
> Add system_error_is_success/1.
> 
> library/io.m:
>       As above.
> 
> library/io.error_util.m:
>       Delete the equivalent operation is_success/1 from here and
>       just use system_error_is_success/1 instead.
> 
> NEWS.md:
>       Announce the new predicate.
> 

That's fine.

Peter