Re-Enable CTRL + ALT + Backspace to Restart X in Ubuntu karmic

As with Ubuntu 9.0.4, the shortcut to disable restarting of X has been disabled in Ubuntu karmic, and the previous method does not work now. Instead go to System --> Preferences --> keyboard --> Layouts --> Layout Options and tick the option as shown in the screenshots. So next time on that hopefully rare occasion X locks up you can now restart X, instead of resorting to holding the power button in.