Description:
------------
comparison const and define.
define() allows expressions as the value.
but const only allows scalar.

Reproduce code:
---------------
const FIRST_CONSTANT = __DIR__.DIRECTORY_SEPARATOR;
// parse error

define('SECOND_CONSTANT', __DIR__.DIRECTORY_SEPARATOR);
// this work

const THIRD_CONSTANT = SECOND_CONSTANT;
// this work too

Expected result:
----------------
const FIRST_CONSTANT = __DIR__.DIRECTORY_SEPARATOR;
// expected same define() work

define('SECOND_CONSTANT', __DIR__.DIRECTORY_SEPARATOR);
// this work

const THIRD_CONSTANT = SECOND_CONSTANT;
// this work too