port/port.tcl: port dependents: Read the dep_map only once
port/port.tcl:
port dependents: Read the dep_map only once

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@44970 d073be05-634f-4543-b044-5fe20cf6d1d6

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