Hande kext:altUrl in the query lib.

Now that we store symbolic links in kext:altUrl the easiest way to
search symlinks is to simply always matchin both nie:url and kext:altUrl
whenever a client asks for nie:url.
This is now done in ComparisonTerm making the class even more complicated.
I doubt anyone else besides me will ever manage to find their way through
that class. I really need to find a way to modularize it...