url: change variable name to be more descriptive

PR-URL: https://github.com/nodejs/node/pull/15551
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

lib/url.js

@@ -71,9 +71,9 @@ ParsedQueryString.prototype = Object.create(null);
 function urlParse(url, parseQueryString, slashesDenoteHost) {
   if (url instanceof Url) return url;
 
-  var u = new Url();
+  var urlObject = new Url();
-  u.parse(url, parseQueryString, slashesDenoteHost);
+  urlObject.parse(url, parseQueryString, slashesDenoteHost);
-  return u;
+  return urlObject;
 }
 
 Url.prototype.parse = function(url, parseQueryString, slashesDenoteHost) {