In the fall, the Assn. of American Railroads said it is likely to cut 93 jobs here. Acme Metals Inc. is in the process of cutting 20% of its 1,500 jobs. Last spring, Quaker Oats Co. swept 300 people-10% of its headquarters staff-from the payroll. And heads continue to roll at AT&T Network Systems in Lisle, as departments pursue their own restructuring and layoff plans.