url: adding WHATWG URL support

Implements WHATWG URL support. Example:

```
var u = new url.URL('http://example.org');
```

Currently passing all WHATWG url parsing tests and all but two of the
setter tests. The two setter tests are intentionally skipped for now
but will be revisited.

PR-URL: nodejs#7448
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>

benchmark/url/new-url-parse.js

@@ -0,0 +1,57 @@
+'use strict';
+const common = require('../common.js');
+const url = require('url');
+const v8 = require('v8');
+
+const bench = common.createBenchmark(main, {
+  type: 'one two three four five'.split(' '),
+  method: ['old', 'new'],
+  n: [25e4]
+});
+
+function useOld(n, input) {
+  // Force-optimize url.parse() so that the benchmark doesn't get
+  // disrupted by the optimizer kicking in halfway through.
+  url.parse(input);
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(url.parse)');
+
+  bench.start();
+  for (var i = 0; i < n; i += 1)
+    url.parse(input);
+  bench.end(n);
+}
+
+function useNew(n, input) {
+  bench.start();
+  for (var i = 0; i < n; i += 1)
+    new url.URL(input);
+  bench.end(n);
+}
+
+function main(conf) {
+  const type = conf.type;
+  const n = conf.n | 0;
+  const method = conf.method;
+
+  var inputs = {
+    one: 'http://nodejs.org/docs/latest/api/url.html#url_url_format_urlobj',
+    two: 'http://blog.nodejs.org/',
+    three: 'https://encrypted.google.com/search?q=url&q=site:npmjs.org&hl=en',
+    four: 'javascript:alert("node is awesome");',
+    //five: 'some.ran/dom/url.thing?oh=yes#whoo',
+    five: 'https://user:pass@example.com/',
+  };
+  var input = inputs[type] || '';
+
+  switch (method) {
+    case 'old':
+      useOld(n, input);
+      break;
+    case 'new':
+      useNew(n, input);
+      break;
+    default:
+      throw new Error('Unknown method');
+  }
+}