url: improve parsing speed

The url.parse() function now checks whether an escapable character is in
the URL before trying to escape it.

PR-URL: https://github.com/joyent/node/pull/8638
[trev.norris@gmail.com: Switch to use continue instead of if]
Signed-off-by: Trevor Norris <trev.norris@gmail.com>

lib/url.js

@@ -318,6 +318,8 @@ Url.prototype.parse = function(url, parseQueryString, slashesDenoteHost) {
     // need to be.
     for (var i = 0, l = autoEscape.length; i < l; i++) {
       var ae = autoEscape[i];
+      if (rest.indexOf(ae) === -1)
+        continue;
       var esc = encodeURIComponent(ae);
       if (esc === ae) {
         esc = escape(ae);