Added <initializer_list> to stdc++.h

[Paolo Carlini]

Ed Smith-Rowland wrote:
> I asked Benjamin Kosnik in a discussion of this very patch and he
> readily agreed.
>
> Sorry for the surprise.  I'm aware of the rules.
No problem, but this kind of decision should be public.
> The patch was discussed although it was possibly hidden under a
> discussion of the aggregation headers proposal of Stroustrup.
>
> I'll add myself to maintainers under the write after approvals.
Ok, thanks.

Paolo.