packet.tcp: Compute offset when packing
packet.tcp: Compute offset when packing

The code previously required the user to manually adjust
the offset when necessary; pack() can now do this itself.

Signed-off-by: Murphy McCauley <4a186f831f9e499082222e927502d182f9e495ec@gmail.com>

noxrepo/pox,noxrepo/pox,noxrepo/pox,pthien92/sdn,pthien92/sdn,MurphyMc/pox,MurphyMc/pox,MurphyMc/pox,pthien92/sdn,MurphyMc/pox,MurphyMc/pox,noxrepo/pox,pthien92/sdn,pthien92/sdn