Indicate that the fall-through in `is_serialized()` is deliberate. fixes #24023.

git-svn-id: https://develop.svn.wordpress.org/trunk@25371 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/functions.php

@@ -282,6 +282,7 @@ function is_serialized( $data, $strict = true ) {
 			} elseif ( false === strpos( $data, '"' ) ) {
 				return false;
 			}
+			// or else fall through
 		case 'a' :
 		case 'O' :
 			return (bool) preg_match( "/^{$token}:[0-9]+:/s", $data );