Description:
------------
ReflectionClass does not respect imported classes. This affects ReflectionClass::__construct(), ReflectionClass::implementsInterface() and ReflectionClass::isSubclassOf().

Reproduce code:
---------------
<?php
namespace Base;
interface IFace
{}

class Impl implements IFace
{}

namespace Other;
use Base::IFace;
use Base::Impl;

$reflected = new ReflectionClass('Impl');

Expected result:
----------------
$reflected is an instance of a ReflectionClass for the class Base::Impl

Actual result:
--------------
ReflectionException: Class Impl does not exist