Description:
------------
I expected 'internal' and not 'Core' to be the index for internal core 
constants. This apparently changed in PHP 5.3.0, yet is not in NEWS or 
documented. Please clarify the situation, as this may have been an 
unintentional change and BC break.

Related: PHP bug #49223

Reproduce code:
---------------
<?php
$constants = get_defined_constants(true);

if (isset($constants['Core'])) {
    echo 'Key "Core" exists, PHP version: ' . PHP_VERSION;
}
if (isset($constants['internal'])) {
    echo 'Key "internal" exists, PHP version: ' . PHP_VERSION;
}


Expected result:
----------------
Key "internal" exists, PHP version: 5.3.2-dev
Key "internal" exists, PHP version: 5.2.8

Actual result:
--------------
Key "Core" exists, PHP version: 5.3.2-dev
Key "internal" exists, PHP version: 5.2.8