Avoid autoloading self and parent in PHP 5.2

Summary: call_user_func(array('parent', 'insert')) issues E_STRICT in 5.1.2 <= PHP < 5.3.0.

Test Plan:

class C extends D {
  function f() {
    call_user_func(array($this, 'self::g'));
  }
  function g() {
    echo "C::g()\n";
  }
}
$c = new C;
$c->f();

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D6427