Description:
------------
constant does not work when using constant class with a class defined in a use statement.

Test script:
---------------
//Foo/Bar.php
namespace Foo;
class Bar
{
  const toto=42;
}

// index.php
use Foo\Bar;
$const = 'toto';
print constant('Bar::'.$const);
//PHP Warning:  constant(): Couldn't find constant 

Expected result:
----------------
42