Retiring ports.php

[Joshua Root]

I think ports.macports.org is already clearly superior to ports.php, so
we should change the Available Ports link to point there. However, we
should not remove ports.php so as not to break existing links. I think
we should make ports.php queries redirect to the corresponding p.m.o URL
when possible (it won't always be possible since ports.php lets you
search more fields).

Thoughts?

- Josh