Add is_comment_feed() to expose ->is_comment_feed. Fixes #10827 props scribu.

git-svn-id: http://svn.automattic.com/wordpress/trunk@12487 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/query.php

@@ -297,6 +297,20 @@ function is_feed () {
 	return $wp_query->is_feed;
 }
 
+/**
+ * Whether current page query is comment feed URL.
+ *
+ * @since 3.0.0
+ * @uses $wp_query
+ *
+ * @return bool
+ */
+function is_comment_feed () {
+	global $wp_query;
+
+	return $wp_query->is_comment_feed;
+}
+
 /**
  * Whether current page query is the front of the site.
  *