Updated links to more information on cookies.

The two linked RFCs are out of date, the one draft link is dead
and rfc6265 is the new canonical Cookie RFC.

Also, cookies are no longer an 'innovation' :D
Fixed links in CGI.pm

Two links did not render properly on CPAN.
The Boulder document no longer exists, and the L<Boulder> perl module
has all the documentation you'd need.
Merge pull request #139 from mbeijen/pod-links

POD links and some documentation tweaks