[v3] Implement resolution of DR 630

[Jason Merrill]

On 07/22/2009 08:25 AM, Paolo Carlini wrote:
> -- Jason, while working on this issue, I noticed that:
>
>      valarray<int>  v1;
>      v1 = { };
>
> compiles just fine in -std=c++0x mode and, for the assignment, ends up
> being selected:
>
>      operator=(const Tp&)
>
> with Tp == 0. On the other hand, in C++03 mode, the snippet doesn't
> compile at all. Could you please confirm the above is the expected
> behavior? Thanks in advance!

Actually, yes, that's what the current draft says should happen.  Though 
it may not be what we want to happen.

Jason