Tuples: draft 1

[Benjamin Kosnik]

>struct swallow_assign
>{
>  template <class T>
>  swallow_assign&
>  operator=(const T&)
>    {return *this;}
>};
>extern swallow_assign ignore;

At the moment, just do

namespace
{ 
	swallow_assign ignore;
};

This will allow us to use this class without figuring out linkage at
this moment, which is something that will require some work.

However, if it's ok with you I'd like to just go ahead and check some
of this stuff in, and then everybody can work from CVS versions.
Sound good?

-benjamin