Comment 20 for bug 1245064

Doing a Google search on this issue led me to this report, as well as the following blog post: http://www.humans-enabled.com/2013/10/ubuntu-1310-enable-controlaltbackspace.html
The author points out that it's possible to access all of these options from a terminal. (Although it would be nice it the GUI was still there...) The command

sudo dpkg-reconfigure keyboard-configuration

brings up a pretty straightforward interface that takes you though about half a dozen keyboard options (compose key, etc). The last option is whether or not to enable Ctrl-Alt-Backspace.