Fix trailing <br>s added in lists with EXTENSION_HARD_LINE_BREAK enabled

[thebaer]

Previously, with EXTENSION_HARD_LINE_BREAK enabled, <li>s would contain unnecessary <br />s at the end of each item. It was especially noticeable by the vertical space this left following an ordered or unordered list.

This fixes that by also stripping trailing <br />s from individual list items when this extension is enabled.

One shortcoming of this patch: it does not completely fix the issue in nested lists, as far as the markup goes -- but the visual issues are gone, at least. I can work on fully fixing the markup if there's interest in that.

Input:

* One
* Two

Paragraph

Previous Result	Fixed Result
<ul> <li>One<br /></li> <li>Two<br /> <br /></li> </ul>   <p>Paragraph</p>	<ul> <li>One</li> <li>Two</li> </ul>   <p>Paragraph</p>