After Elvis Dumervil signed with the 49ers in June, he looked at general manager John Lynch and congratulated him. “I said, ‘Listen, you just got the steal of this free agency,’” Dumervil recalled. “‘Without a doubt.’” Dumervil, 33, clearly doesn’t harbor any, but there are doubts surrounding him this summer. The outside linebacker enters his 12th season with 99 sacks (third among active players), five Pro Bowl berths … and a recent history that suggests the quarterback menace is now being manhandled by Father Time. Even Lynch acknowledged the addition of Dumervil, the second-oldest player on the roster, was odd, on the surface.