Provide a user-space application for multiplexing traffic from multiple
ports across an IP tunnel on another port.

How To Use:
-----------
consider this example:

Machine A is the border machine. we want to capsulate and forward 
traffic from eth1 to machineB which in turn decapsulates the traffic
and forwards it to virtual port tap1. Trafic from eth2 on machineA
will be encapsulated and forwarded to machineC which in turn will be
decapsulated and forwarded to tap0. note that the tunnels are 
bidirectinonal.

  |eth1  |eth2
-------------		    eth0 ------------- 
| Machine A | ------------------ | Machine B |
-------------| eth0              -------------
	     |			       |output to tap port tap1
	     |			       |
	     |eth0
	------------
	| Machine C |
	-------------
	     |output to tap port tap0
	     |

Here are the commands that should run on these machines:

on MachineA:
./capsulator -f machineB_ip_addr, machineC_ip_addr -t eth0 -b eth1#20 -b 
eth2#21
[ Note that order of writing IP addresses in -f is the same as order of listing
  border ports (-b/-vb), ie. machineB receives eth1 traffic, hence the order 
  above]

on MachineB:
./capsulator -f machineA_ip_addr -t eth0 -vb tap1#20

on MachineC:
./capsulator -f machineA_ip_addr -t eth0 -vb tap0#21

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