preparing for a new release

[Joshua Root]

I'm thinking we should aim to do a release roughly concurrent with Lion.
Most of the tickets in the 2.0.0 milestone are closed already, and none
of the remaining ones looks too disruptive, so if nobody objects, I'll
make the branch and do a first beta release in a couple of days.

Someone with a Tiger install really needs take a look at
<https://trac.macports.org/ticket/29592>. If it's reproducible, we need
to fix it, or at least make base refuse to install on Tiger so
selfupdate doesn't break anyone's ports.

- Josh