init(pthreadPriorityCommand:previousVoucher:content:)
Creates a new voucher attribute recipe for a POSIX thread priority command.
init(pthreadPriorityCommand: Mach.VoucherPthreadPriorityAttributeRecipeCommand, previousVoucher: Mach.Voucher = Mach.Voucher.Nil, content: Data? = nil)