Before intersecting two port lists, make each list unique with respect to the port's fullname. In uniqueing the lists, always take the first item found.
Before intersecting two port lists, make each list unique with respect
to the port's fullname. In uniqueing the lists, always take the first
item found.

This may solve some issues with ambiguity of selection where a portlist
contains entries from multiple repositories. A better solution may
be to ensure that entries returned in a repository search are unique to 
begin with.

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@88179 d073be05-634f-4543-b044-5fe20cf6d1d6

neverpanic/macports-base,macports/macports-base,neverpanic/macports-base,macports/macports-base,danchr/macports-base,danchr/macports-base