XoopsForm radio/checkbox with "label" tag

This patch makes the classes XoopsFormRadio, XoopsFormRadioYN
and XoopsFormCheckBox to render radio buttons / check boxes along
with "label" tags like the following:

<input type="radio" id="foo1" name="foo" value="bar"/><label for="foo1">HEY</label>

In the example above you can activate a radio button by clicking the text
"HEY", tested under Firefox/Mozilla/Opera/IE.

The ptach files are based on the files from XOOPS 2.2 RC.