[framework] Experimental support for IPv6

[H D Moore]

The development version (trunk) of Metasploit 3 now supports IPv6 sockets. 
All auxiliary and exploit modules should now support IPv6 addresses if 
the host system supports AF_INET6. 

The catch is that until we have IPv6-aware payloads (bind/reverse/etc), 
the exploits will not be that useful on IPv6 networks. Payloads 
like "adduser" will work, but all of the standard "remote shell" modules 
are hardcoded for IPv4 sockets.

If testing goes well, IPv6 support will be merged into the next major 
release (3.1). 

-HD

-- example ---

# Choose the HTTP version scanning module
msf > use auxiliary/scanner/http/version

# Target the /120 where www.ipv6experiment.com lives
msf auxiliary(version) > set RHOSTS 2001:4978:1:110:0:ac:ce55:1b1e/120
RHOSTS => 2001:4978:1:110:0:ac:ce55:1b1e/120

# Run the module
msf auxiliary(version) > run
[*] 2001:4978:0001:0110:0000:00ac:ce55:1b1e is running lighttpd/1.4.13
[*] Auxiliary module execution completed