Fix a MinGW warning in libiberty/strerror.c

[Eli Zaretskii]

> Date: Fri, 16 Jan 2015 16:39:20 -0500
> From: DJ Delorie <dj@redhat.com>
> CC: ktietz70@googlemail.com, gcc-patches@gcc.gnu.org,
>         gdb-patches@sourceware.org
> 
> 
> > Thanks.  Do I need to hear from someone else approving this, or can I
> > go ahead and commit?
> 
> Go ahead and commit.

Thanks.

Last-minute thought, in case I'm confused: you mean commit to the
sourceware Git repo, right?  If not, where?