Mention addition of TR1 to C++ for GCC-4.0.0

[Paolo Carlini]

Joe Buck wrote:

>Nevertheless, we could use a note documenting the parts of TR1 that will
>be in 4.0.0, how to use it, etc., and make sure to warn people that it is
>experimental (meaning that the libstdc++ team makes no promises about
>backward compatibility, so the users might have to revise their programs
>later on should the committee make changes).
>  
>
I concur and would like to add that some facilities, like <tuple> 
prepared by
Chris, are already rather close to the final form!

Paolo.