update RELEASE_URL to 1.8.0
update RELEASE_URL to 1.8.0

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@56457 d073be05-634f-4543-b044-5fe20cf6d1d6

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