Fix validation issue - add required="required"

Joomla 2.5 output
```
<input type="text" size="30" class="inputbox required" value="" id="jform_title" name="jformtitle" aria-required="true" required="required">
```

3.2. after recent changes
```
<input type="text" size="30" class="inputbox" value="" id="jform_title" name="jformtitle">
```

The above patch adds required back for fields that are marked required