discard annoying nodejs warning

tools/node.js

@@ -1,4 +1,12 @@
+var save_stderr = process.stderr;
 var fs = require("fs");
+
+// discard annoying NodeJS warning ("path.existsSync is now called `fs.existsSync`.")
+var devnull = fs.createWriteStream("/dev/null");
+process.__defineGetter__("stderr", function(){
+    return devnull;
+});
+
 var vm = require("vm");
 var sys = require("util");
 var path = require("path");
@@ -10,6 +18,10 @@ var UglifyJS = vm.createContext({
     MOZ_SourceMap : require("source-map")
 });
 
+process.__defineGetter__("stderr", function(){
+    return save_stderr;
+});
+
 function load_global(file) {
     file = path.resolve(path.dirname(module.filename), file);
     try {