Remapping Caps Lock to Compose

Because I now and then need to use scandinavian letters despite using US Dvorak as my layout, I would like to use Caps Lock as a compose key. (I don't need Caps Lock at all, I'm not a forum troll) How would one accomplish this? Using Linux Mint 17 with xfce, if that makes a difference. For the record, I am the only user of this PC, and would prefer to have this be the system default, mainly in xorg, but also in tty if that's not too much drudgery.