Add @static* annotations where they are missing.

Initialize all static vars that are not, most to `null`.

See #32444.


git-svn-id: https://develop.svn.wordpress.org/trunk@32650 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/class-wp-list-table.php

@@ -900,6 +900,8 @@ class WP_List_Table {
 	 * @since 3.1.0
 	 * @access public
 	 *
+	 * @staticvar int $cb_counter
+	 *
 	 * @param bool $with_id Whether to set the id attribute or not
 	 */
 	public function print_column_headers( $with_id = true ) {