Newsday reports that the number of confirmed cases of salmonella at Princeton University continues to grow.  The university said today that there are now 22 confirmed cases -- 20 students and two staff.  Health officials have been investigating more than 70 other cases of stomach problems at the school that may be related to the bacteria.  The number of confirmed cases is four times what it was a week ago.  No source has been determined. But a salad bar and a Mexican food station at the campus center's dining facility remain closed as a precaution.