Make entire row of doc search results clickable

By adding empty `after` content that clears and is `display: block`.
Technique found here: https://stackoverflow.com/a/7817313/51683

Now any part of a documentation search result that is highlighted when
you hover over it should also be clickable.

src/librustdoc/html/static/rustdoc.css

@@ -615,6 +615,11 @@ a {
 .content .search-results td:first-child a {
 	padding-right: 10px;
 }
+.content .search-results td:first-child a:after {
+    clear: both;
+    content: "";
+    display: block;
+}
 .content .search-results td:first-child a span {
 	float: left;
 }