port.tcl: print a less alarming and more user-friendly message if the portlist given to upgrade is empty
port.tcl: print a less alarming and more user-friendly message if the portlist given to upgrade is empty

Previously "port upgrade outdated" with no outdated ports printed "Error: No
ports matched the given expression." which is correct but hard to understand
for users who don't know how to use the expression system and thus bad from
a UX POV.

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@105529 d073be05-634f-4543-b044-5fe20cf6d1d6

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