Comments: add date column to WP_Comments_List_Table to allow sorting and to break out the date/time from the comment content column.

Props jshreve.
Fixes #15520.

Built from https://develop.svn.wordpress.org/trunk@34504


git-svn-id: http://core.svn.wordpress.org/trunk@34468 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/list-tables.css

@@ -386,6 +386,10 @@ table.media .column-title .filename {
 	width: 20%;
 }
 
+#comments-form .fixed .column-date {
+	width: 14%;
+}
+
 #commentsdiv.postbox .inside {
 	margin: 0;
 	padding: 0;