Comment 60 for bug 1357895

Sorry about that, we just updated Gala to handle modifier-only keybindings again, there will be an update to the keyboard plug to set them up again, if you want a quick solution now, you can use dconf-editor and go to org.gnome.desktop.input-sources and add the option you want to xkb-options, the available options can be seen with 'grep grp: /usr/share/X11/xkb/rules/evdev.lst' (not all of them have been implemented but the most common should work fine).