[selectors] Clean up 'new sections' section of Changes section.

This makes four changes:
 * it links to the new sections
 * it drops the Evaluating a Selector item, since that's a subsection of the API Hooks section that's already listed
 * it fixes the generation of Issues by adding a newline before them
 * it links to the github issue for the issue on selector evaluation, which includes a link to the www-style message previously linked

This is in preparation for actually fixing that github issue,
w3c#720

Author: dbaron

selectors/Overview.bs

@@ -3551,11 +3551,12 @@ Changes</h2>
 		Issue: Semantic definition should probably move back here.
 		<li>Added new sections:
 			<ul>
-				<li>Evaluating a Selector
-				Issue: https://lists.w3.org/Archives/Public/www-style/2015Mar/0432.html
-				<li>Data Model
+				<li>[[#data-model]]
+
 				Issue: Need to define tree for XML.
-				<li>API Hooks
+				<li>[[#api-hooks]]
+
+				Issue: <a href="https://github.com/w3c/csswg-drafts/issues/720">selector matching should be specified as being from right to left, not left to right</a>
 			</ul>
 		<li>Removed restriction on combinators within '':matches()'', '':not()'', '':nth-match()'', and '':nth-last-match()''.
 			Issue: Do we have implementations of this? If not, maybe it's better to keep the restriction for level 4?