Add <initializer_list> to stdc++.h and ruminations on aggregation headers

[Jonathan Wakely]

2009/9/25 Ed Smith-Rowland:
>
> Of course these aggregation headers are not in the std yet ;-).  These are
> just to think about.

The std-checked proposal said that the checked code must be ABI
compatible with non-checked, so there was considerable opposition to
it.  It would be premature to change libstdc++ to match anything in
that proposal.