BackgroundTasks iOS 12.4 to 13.0 API Differences

BGDefines.h
Added #def BG_EXTERN
BGTask.h
Added BGTask
BGTaskRequest.h
BGTaskScheduler.h
Added BGTaskSchedulerErrorCode
Added BGTaskSchedulerErrorCodeUnavailable
Added BGTaskSchedulerErrorCodeTooManyPendingTaskRequests
Added BGTaskSchedulerErrorCodeNotPermitted