Populate ReflectionClass::$this on creation.

ReflectionClass does not populate $info until a function such as getMethods() is called. This causes the ReflectionClass instance to compare differently before and after these methods are called, causing several tests in the symfony Validator component to fail (AnnotationLoaderTest.php).

Repro code:
```
<?php
 class Foo {
 }
 
 $mirror = new ReflectionClass("ReflectionClass");
 $foo_reflectorA = new ReflectionClass("Foo");
 $foo_reflectorB = new ReflectionClass("Foo");
 $foo_reflectorB->getMethods();
 $info_property = $mirror->getProperty("info");
 $info_property->setAccessible(true);
 $infoA = $info_property->getValue($foo_reflectorA);
 $infoB = $info_property->getValue($foo_reflectorB);
 var_dump($infoA == $infoB);
```

Expected output:
```
bool(true)
```

Actual output:
```
bool(false)
```