[patch] : Improve std::search on v7

[Paolo Carlini]

Gabriel Dos Reis wrote:

>I did not mean to sound funny.  I just did get nothing from what you
>said. But if you think it does not matter I understand what you wanted
>to say, that is OK.  If you think you can explain, that is OK too.
>  
>
Ok... But please, don't say -nothing-, how this can be ever possible, as
a serious statement?!?

You said there are problems with virtuals. Ok, let's deal with that in a
radical way: we check whether the base class at issue, Compare, is
*really* empty, tr1::is_empty is false in case of virtuals, and only in
those safe cases, we *derive* from it and exploit EBO.

Can you also imagine issues with EBO when no virtuals are involved?
Otherwise we would be ok.

... besides unions, which we cannot detect without compiler support, sadly.

Paolo.