try to determine the number of cores for number of parallel build jobs (if those are set to '0')
try to determine the number of cores for number of parallel build jobs (if those are set to '0')

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@30739 d073be05-634f-4543-b044-5fe20cf6d1d6

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