Gerber Products said it plans to suspend baby-food production at its Oakland food-processing facility and lay off about 270 employees effective Nov. 15 . . . Apple Computer said it plans to lay off more than 100 employees at its suburban Dallas manufacturing plant beginning June 1, due to the firm’s decision to cease production of the Macintosh XL business computer . . . Prime Computer said it is introducing a multiuser operating system called Primix that is based on AT&T;'s Unix System V.