Lion disk image for MacPorts 2.0.0-rc1

[Joshua Root]

There's now a Lion installer available along with the rest:

<https://distfiles.macports.org/MacPorts/testing/MacPorts-2.0.0-rc1-10.7-Lion.dmg>

One known issue: 'port pkg' may not work correctly on Lion with dropped
privileges. The symptom is that the built package does not install any
files. Some other targets such as mpkg and dmg depend on pkg and are
therefore also affected.

- Josh