Description:
------------
Two new functions that make a class inherit from another class (if it does not have a parent class, yet) and implement an interface (if it implements the required methods), respectively, would be nice.

Reproduce code:
---------------
<?php
class ParentClass {}
class ChildClass {}

runkit_inherit_class('ChildClass', 'ParentClass');

interface I {public function doSomething();}
class C {public function doSomething() {}}

runkit_implement_interface('C', 'I');
?>

Expected result:
----------------
<?php
class ChildClass extends ParentClass {}
class C implements I {public function doSomething() {}}
?>