New 'CHANGES' section for RFC's

I'd like to suggest a CHANGES section for differences between versions
of RFC's. This could go right after VERSION:


=head1 VERSION

...
  Version: 2
...

=head1 CHANGES

- added foo() function
- removed $bar attribute


Especially as the number and length of RFC's is increasing, this helps
keep up. I think only changes between consecutive versions need be
mentioned, since the main point would be to help email scanning.

-Nate

• New 'CHANGES' section for RFC's by Nathan Wiger