TR1 copyright

[Matt Austern]

Mike Stump pointed out that there was a potential error in the
copyright notice for my new TR1 unordered associative container
headers.  I misunderstood him; I thought he was just talking about the
same problem Paolo noticed, and that I fixed, i.e. the date.

The actual issue, which is shared by all of the TR1 headers (not
surprisingly; I cut-and-paste, and I'm sure most people did) is that
the headers say they're covered by the GPL.  Do we really mean to do
that?  libstdc++ itself is covered by GPL-with-exception.  But the
exception for free software libraries isn't there in the TR1 headers.

I'm guessing this was just a goof, not a deliberate policy change for
TR1, but best to make sure.

         --Matt