[themes] Highlighting active leaf in book navigation.

[Stephen Wills]

I have css elements to color the individual page titles in the block  
book-navigation and as I hover over them they changes colors and all  
is right with the world except I would like to highlight the page  
title of the currently viewed page.  I am wondering if anyone knows a  
CSS trick that will redefine the .leaf class when the anchor element  
it encloses is of class=active?

Thanks.