Description:
------------
ReflectionParameter::getDefaultValueConstantName() returns wrong value in namespace context,
in particular, invocated in a namespace, it returns wrong value for global constants

Test script:
---------------
<?php
namespace {

    define('SOME_CONSTANT', 1);
}

namespace Some\Name\Space {

    use ReflectionFunction;

    $reflection = new ReflectionFunction(function ($const = PHP_EOL, $const2 = SOME_CONSTANT) {
    });
    echo $reflection->getParameters()[0]->getDefaultValueConstantName() . PHP_EOL;
    echo $reflection->getParameters()[1]->getDefaultValueConstantName() . PHP_EOL;
}


Expected result:
----------------
PHP_EOL
SOME_CONSTANT


Actual result:
--------------
Some\Name\Space\PHP_EOL
Some\Name\Space\SOME_CONSTANT