patch recieved from Peter Van Eeckhout

git-svn-id: file:///home/svn/framework3/trunk@11898 4d416f70-5f16-0410-b530-b9f4589650da

modules/payloads/singles/windows/messagebox.rb

@@ -85,7 +85,6 @@ module Metasploit3
 	;store function address at ebx+08
 	mov [ebp+0x8],eax
 EOS
-
 		doexit = <<EOS
 	xor eax,eax		;zero out eax
 	push eax		;put 0 on stack
@@ -102,6 +101,12 @@ EOS
 			getexitfunc = ''
 		end
 		
+		# if exit is set to none, then make exit empty
+		if datastore['EXITFUNC'].upcase.strip == "NONE"
+			getexitfunc = ''
+			doexit = ''
+		end
+
 		# Generate code to get ptr to Title
 		marker_idx = strTitle.length - 1
 		strPushTitle = string_to_pushes(strTitle, marker_idx)