Lua 5.2 upgrade [1] for NSE.

[1] http://seclists.org/nmap-dev/2012/q2/34

scripts/sniffer-detect.nse

@@ -1,3 +1,7 @@
+local nmap = require "nmap"
+local stdnse = require "stdnse"
+local string = require "string"
+
 description = [[
 Checks if a target on a local Ethernet has its network card in promiscuous mode.
 
@@ -10,7 +14,6 @@ http://www.securityfriday.com/promiscuous_detection_01.pdf.
 -- Host script results:
 -- |_ sniffer-detect: Likely in promiscuous mode (tests: "11111111")
 
-require 'nmap'
 
 author = "Marek Majkowski"
 license = "Same as Nmap--See http://nmap.org/book/man-legal.html"