new concept checks and the 3.0 ABI

[Joe Buck]

> | Note that http://www.codesourcery.com/cxx-abi/ talks about the multivendor
> | ABI -- we never signed up, nor should we sign up, to having our library
> | interoperable with other vendors' libraries.
> 
> If you don't want GCC/g++ comply to the multivendor ABI, that is not an
> issue I'll dispute with you.  It *is* the fact that ABI is implemented
> in the compiler.

No, that's not what I'm saying.  The ABI as described is fine.  I'm just
saying that I see no reason to force our library to be exactly the same
as everyone else's.