Fix: & in url of newsfeed not escaped Ref: #4862

#### Steps to reproduce the issue
Make a module "Feed display" and take for eg. this as feed Url: http://www.zdnet.de/feed/

#### Expected result

The above feed gives URLs like

http://www.zdnet.de/88208524/fitbit-plant-fitness-smartwatch-mit-gps/?utm_source=rss&utm_medium=rss&utm_campaign=rss

In line 104 of /modules/mod_feed/tmpl/default

```php
<?php echo $uri; ?>
```

should be replaced with

```php
<?php preg_replace('/&(?!amp;)/', '&amp;', $uri); ?>
<?php echo $uri; ?>
```

also in line 66 of the same file.

#### Actual result

& don't get replaced.

#### System information (as much as possible)

Joomla! 3.3.6

#### Additional comments

See: https://github.com/joomla/joomla-cms/issues/4862 by @dirk-graetz