[v3] C++0x type_traits post-oxford additions

[Benjamin Kosnik]

> For make_(un)signed floating point types were not included because:
> 
> *  I wasn't aware of any use cases.
> 
> *  The semantics of make_signed<double>::type and 
> make_unsigned<double>::type didn't seem obviously clear.
> 
> *  As I recall when I surveyed my own implementation, and other 
> implementations I found, no one had applied this functionality to 
> floating point types (so no existing practice).
> 
> *  make_(un)signed<long double> seems fragile / non-portable.
> 
> That being said, please feel free to send me a defect report if you 
> would like to see make_(un)signed applied to floating point types.

Thanks for clarifying this Howard.

-benjamin