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