benchmark: add benches for fs.stat & fs.statSync

Add very simple benchmarks for `fs.stat` and `fs.statSync` as
well as `fs.lstat` and `fs.lstatSync` based on the `readdir`
benchmarks.

PR-URL: https://github.com/nodejs/node/pull/8338
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

benchmark/fs/bench-stat.js

@@ -0,0 +1,23 @@
+'use strict';
+
+const common = require('../common');
+const fs = require('fs');
+
+const bench = common.createBenchmark(main, {
+  n: [1e4],
+  kind: ['lstat', 'stat']
+});
+
+
+function main(conf) {
+  const n = conf.n >>> 0;
+
+  bench.start();
+  (function r(cntr, fn) {
+    if (cntr-- <= 0)
+      return bench.end(n);
+    fn(__filename, function() {
+      r(cntr, fn);
+    });
+  }(n, fs[conf.kind]));
+}

benchmark/fs/bench-statSync.js

@@ -0,0 +1,21 @@
+'use strict';
+
+const common = require('../common');
+const fs = require('fs');
+
+const bench = common.createBenchmark(main, {
+  n: [1e4],
+  kind: ['lstatSync', 'statSync']
+});
+
+
+function main(conf) {
+  const n = conf.n >>> 0;
+  const fn = fs[conf.kind];
+
+  bench.start();
+  for (var i = 0; i < n; i++) {
+    fn(__filename);
+  }
+  bench.end(n);
+}