Lua 5.2 upgrade [1] for NSE.

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

scripts/oracle-enum-users.nse

@@ -1,3 +1,14 @@
+local math = require "math"
+local nmap = require "nmap"
+local shortport = require "shortport"
+local stdnse = require "stdnse"
+local string = require "string"
+local table = require "table"
+local tns = require "tns"
+local unpwdb = require "unpwdb"
+
+local openssl = stdnse.silent_require "openssl"
+
 description = [[
 Attempts to enumerate valid Oracle user names against unpatched Oracle 11g
 servers (this bug was fixed in Oracle's October 2009 Critical Patch Update).
@@ -32,11 +43,6 @@ author = "Patrik Karlsson"
 license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
 categories = {"intrusive", "auth"}
 
-require 'shortport'
-require 'unpwdb'
-require 'stdnse'
-stdnse.silent_require 'openssl'
-require 'tns'
 
 portrule = shortport.port_or_service(1521, 'oracle-tns' )