CL-UNIFICATION system and package names aligned.

NS rightly complains here about system and package names for CL-UNIFICATION. I fixed the problem in CVS (it should take a little to propagate to Quicklisp) by adding the proper nickname to the package, i.e., "CL-UNIFICATION". My excuse is that this was a left over from a few years back when nomenclature had not been as settled. :)