fix __filename and __dirname on server

lib/extension-cjs.js

@@ -47,12 +47,16 @@ function cjs(loader) {
         dirname.pop();
         dirname = dirname.join('/');
 
+        // if on the server, remove the "file:" part from the dirname
+        if (System._nodeRequire)
+          dirname = dirname.substr(5);
+
         var globals = loader.global._g = {
           global: loader.global,
           exports: exports,
           module: module,
           require: require,
-          __filename: load.address,
+          __filename: System._nodeRequire ? load.address.substr(5) : load.address,
           __dirname: dirname
         };