Orange County Mayor Jerry Demings joined historians in downtown Orlando on Sunday to mark the county’s 200th birthday.Speaking at the Orange County Regional History Center, Demings said the occasion was not just about looking back, but forward as well.“We look ahead to the next two hundred years we will build together,” Demings said. “Our county’s history is still being written.”Established on Dec. 29, 1824, as “Mosquito County,” the original te…