Update NEWS for MPX support in the dynamic linker

[Markus Trippelsdorf]

On 2014.08.08 at 11:00 -0700, Roland McGrath wrote:
> > Please note that this issue is _not_ fixed in 3.9. There is no official
> > valgrind release with the fix available at the moment.
> 
> You said it's fixed in trunk, though.  So there is some forthcoming version
> we can name that will have it fixed.  Is that 3.10?

I don't know. But changing "...affect Valgrind versions prior to 3.9" to
"...affect Valgrind versions up to 3.9" should be enough.

-- 
Markus