Type: (set (const :background (const :foreground) (const :underline))
Default value: (:background)
An attribute to use to indicate the current item.
This is looked up in the current dimension, to get the value to set it
to. For example, if versor-item-attribute is
:background is looked up in the current dimension, to find the
colour to set the background to.
You can only use this from Emacs 21 onwards.