Update src/jquery.autocomplete.js

Using the native JSON.parse built-in function in the browsers if it's available.
Adds more security to it, so the autocomplete is less prone to XSS attacks.

src/jquery.autocomplete.js

@@ -361,6 +361,9 @@
             var response;
 
             try {
+                if (typeof(JSON) != "undefined" && typeof(JSON.parse) != "undefined")
+                    response = JSON.parse(text);
+                else
                     response = eval('(' + text + ')');
             } catch (err) {
                 return;