selfupdate warning when port selfupdate

[informatimago (Pascal J. Bourguignon)]

newton:~ root# port selfupdate Warning: port definitions are more than two weeks old, consider using selfupdate

I think this is the most exasperating thing that may happen, to be told what to do when you're doing it. Mothers and wifes are particularly prone to this, we definitely DO NOT WANT to have it from programs!

So please add a little test to skip it when we're doing it!