Even though TrueTypeFont is marked as depreciated it can still be used.
UnicodeFont isn't yet part of Slick-Util, so to use it you'll need to use the Slick2D Jar (slick.jar).
Basically its an issue for the Slick developers to fix, either they should un-depreciate TrueTypeFont or replace it with UnicodeFont in the Slick-Util package.