[PATCH, libstdc++/testsuite, ping2] 29_atomics/atomic/65913.cc: require atomic-builtins rather than specific target

[Thomas Preudhomme]

On Wednesday 29 June 2016 21:58:40 Jonathan Wakely wrote:
> On 29/06/16 13:49 -0700, Mike Stump wrote:
> >Please include the libstdc++ list, they don't all read the other list.
> 
> And the documentation clearly says (in two places) that all libstdc++
> patches must go to the libstdc++ list.

Oops my apologize, I did not think of libstdc++ has a separate component than 
GCC. I'll keep that in mind for next time.

Committed now.

Best regards,

Thomas