Fix warning in posix/bug-regex31.c

[Ondřej Bílka]

On Tue, Nov 25, 2014 at 05:53:38PM +0000, Joseph Myers wrote:
> This patch fixes a "set but not used" warning in posix/bug-regex31.c.
> A variable res stored an indication of whether the test behaved as
> expected, but was then ignored and the test returned 0 unconditionally
> (as an mtrace test, the auxiliary test for leaks could still have
> failed if that bug was present).  This patch makes the test return
> res.
> 
> Tested for x86_64.
> 
looks ok.