Lua 5.2 upgrade [1] for NSE.

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

scripts/dns-srv-enum.nse

@@ -1,3 +1,11 @@
+local coroutine = require "coroutine"
+local dns = require "dns"
+local nmap = require "nmap"
+local stdnse = require "stdnse"
+local tab = require "tab"
+local table = require "table"
+local target = require "target"
+
 description = [[
 Enumerates various common service (SRV) records for a given domain name.
 The service records contain the hostname, port and priority of servers for a given service.
@@ -54,9 +62,6 @@ author = "Patrik Karlsson"
 license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
 categories = {"discovery", "safe"}
 
-require 'dns'
-require 'tab'
-require 'target'
 
 local arg_domain = stdnse.get_script_args(SCRIPT_NAME .. ".domain")
 local arg_filter = stdnse.get_script_args(SCRIPT_NAME .. ".filter")
@@ -171,4 +176,4 @@ action = function(host)
 	table.sort(result, function(a,b) return a.name < b.name end)
 	
 	return stdnse.format_output(true, result)
-end
+end