New tools for using Emacs as an IDE, including navigation across a project and automatic Makefile generation. New major mode for editing JavaScript source. The mouse is hidden while the user is typing.

The current version is in the future, and is most likely a joke on the extremely long time between the release of 21.3 and 22.1. I can't easily find any binary versions of this available on the web, but the URL I give is where you can download the source and build it yourself (which I have done).