Commit corresponding to Google 20130816 images

Overdue PR here: This revision of the repository was used for the v20130816 Google Compute Engine images, which after testing (delayed for unrelated reasons) were published on September 4.

Google's APT repository had not yet been GPG-signed, though it is now, so these commits don't work any more. I have another commit ready that adds handling for Google's GPG key, but to keep this PR cleanly matching the 20130816 images I'll leave that for a subsequent PR.