RETRENCHING. Northern Illinois University faces the problem, common these days in the state-tolerated universities, of making do with less. The student newspaper has a few suggestions for saving money, which are offered as a poll. (In case the poll is delinked, the suggestions are to lease some empty dorm space as a prison, to turn off the lights at the athletic fields when they're not in use, to run fewer buses, and to sell advertising space on buildings.) I have a few suggestions of my own, which I will post by week's end.