http: replace util._extend() with [].slice()

PR-URL: #634
Reviewed-BY: Nicu Micleușanu <micnic90@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>

lib/http.js

@@ -8,7 +8,7 @@ exports.IncomingMessage = require('_http_incoming').IncomingMessage;
 
 
 const common = require('_http_common');
-exports.METHODS = util._extend([], common.methods).sort();
+exports.METHODS = common.methods.slice().sort();
 
 
 exports.OutgoingMessage = require('_http_outgoing').OutgoingMessage;