isr_admin: Avoid integer overflow in makeparcel
isr_admin: Avoid integer overflow in makeparcel

- Fix "isr_admin makeparcel" on 32-bit systems for parcels 4 GB or larger

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr