Fix bug https://trac.macports.org/ticket/10674.
Fix bug https://trac.macports.org/ticket/10674.

port installed, active, list, and search all behaved poorly if given
a pseudo port that evaluated to nothing. The root problem was that the
argument parsing code could not tell the difference between no arguments
and arguments that evaluated to a null set.

The change puts a hack in that sets a global option if there are indeed
no arguments to an action, to allow us to distinguish this case.

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@25789 d073be05-634f-4543-b044-5fe20cf6d1d6

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