Lua 5.2 upgrade [1] for NSE.

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

scripts/http-trace.nse

@@ -1,3 +1,8 @@
+local http = require "http"
+local nmap = require "nmap"
+local shortport = require "shortport"
+local stdnse = require "stdnse"
+
 description = [[
 Sends an HTTP TRACE request and shows if the method TRACE is enabled. If debug is enabled, it returns the header fields that were modified in the response.
 ]]
@@ -24,9 +29,6 @@ license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
 
 categories = {"vuln", "discovery", "safe"}
 
-require "shortport"
-require "stdnse"
-require "http"
 
 portrule = shortport.http