[Patch] Fix glibc testing with GCC 4.9 compiler

[Florian Weimer]

* Steve Ellcey:

> On Thu, 2016-02-25 at 17:49 +0100, Florian Weimer wrote:
>> * Steve Ellcey:
>> 
>> > I was testing glibc on a machine with GCC 4.9.2 and the tests died due
>> > to a warning in string/tester.c.  This routine has a DIAG_IGNORE for
>> > -Wmemset-transposed-args at GCC 5.0 and above but this warning is also
>> > given by my GCC 4.9.2 compiler.  This patch fixed the problem for me,
>> > is it OK to check it in?
>> 
>> I think this breaks the build for everyone with a 4.9 compiler which
>> does not support -Wmemset-transposed-args.  Wasn't this a
>> Debian-specific backport?
>
> That is possible, I wasn't aware this was a backport.

I looked agained, and yes, it's a backport.

I think this would need a configure check for detection because you
can't infer it from the reported compiler version.