Patch for s390x support

[Maxim Dounin]

Hello!

On Mon, Oct 12, 2015 at 05:23:04PM +0000, Neale Ferguson wrote:

> Hi,
> I would like to contribute the a fix to enable the Linux s390x platform.
> The fix was built against today’s mercurial master and pertains to the gcc
> atomic functions. I note the other architectures use inline assembler
> rather than the gcc builtin operations. Is this for historical reasons?

GCC builtin atomic operations are used when available, grep 
NGX_HAVE_GCC_ATOMIC for details.

-- 
Maxim Dounin
http://nginx.org/