Add std::unordered_* C++11 allocator support

[Jonathan Wakely]

On 17 March 2013 11:04, Paolo Carlini wrote:
> Hi,
>
>
> On 03/15/2013 09:45 PM, François Dumont wrote:
>>
>> Hello
>>
>>     I think I have completed support of C++11 allocators in unordered
>> containers.
>
> Thanks. I think Jon can review this patch of yours much better than me.

Yes, I'm working through it :-)
It looks great so far.

There's no rush because I don't think we should commit it to trunk
until after 4.8.0 is released, so the unordered container code doesn't
diverge on trunk and the 4.8 branch until it's released, just to ease
debugging if a problem turns up in a release candidate.