[Patch] Implement Option 3 of DR 431

[Howard Hinnant]

On Dec 20, 2005, at 2:26 PM, Paolo Carlini wrote:

> the below is what I'm finishing testing, versus v7-branch, but we  
> agreed
> to have it in mainline too.

Caution for mainline:  C++03 allocators are not required to be  
swappable (they have copyconstructible but lack copyassignable).  In  
practice this doesn't appear to be a major problem, and can be easily  
fixed by adding a swap to your non-assignable allocator.  Just  
thought I'd better mention it.

> Straightforward, I think, given the existing
> bits in the containers: most of the time I spent preparing the
> testcases, fiuuuuuuuuu ;)

Looks great!

-Howard