[v3] traits duplicate removal

[Paolo Carlini]

Benjamin Kosnik wrote:

>>Note that the warning is *not* suppressed by the pragma system headers, 
>>I'm afraid we have to factor out the numeric_traits class...
>>    
>>
>
>Bummer.
>
>Maybe just do
>
>namespace __numeric_traits
>{
>	// stuff
>}
>
>or just kill class __numeric_traits entirely and put them into __gnu_cxx as constants?
>  
>
You choose, really... Thanks, anyway.

Paolo.