first of all, you cant upgrade your x-chat to latest version if you are using fiesty fawn. The latest version of x-chat nowadays is xchat 2.8.4
Currently, the latest version supported with fiesty fawn is xchat 2.8.0 - so there is 4 version behind the latest one. So to get the new xchat installed in your feisty fawn, all you have to do is:
- wget http://www.xchat.org/files/source/2.8/xchat-2.8.4.tar.bz2
- tar xjvf xchat-2.8.4.tar.bz2
- then go into folder xchat-2.8.4 : cd xchat-2.8.4/
- run script configure: ./configure
- sudo make install
- then start the xchat from your Application menu.
have fun with Ubuntu!