Description:
------------
A new interface "Sortable" and implementation of it on ArrayObject and ArrayIterator.

I could only get 5.6.3 to compile on my setup, so I hope someone can "port" it to 5.6. I've also made some unit tests for the new feature.

I'm not sure if my implementation is "the best solution" (tm), but I hope that I've at least done some footwork.

Test script:
---------------
$o = new ArrayObject(array(3,2,1));

var_dump($o);
sort($o);
var_dump($o);


Expected result:
----------------
object(ArrayObject)#1 (1) {
  ["storage":"ArrayObject":private]=>
  array(3) {
    [0]=>
    int(3)
    [1]=>
    int(2)
    [2]=>
    int(1)
  }
}
object(ArrayObject)#1 (1) {
  ["storage":"ArrayObject":private]=>
  array(3) {
    [0]=>
    int(1)
    [1]=>
    int(2)
    [2]=>
    int(3)
  }
}

Actual result:
--------------
class ArrayObject#1 (1) {
  private $storage =>
  array(3) {
    [0] =>
    int(3)
    [1] =>
    int(2)
    [2] =>
    int(1)
  }
}

Warning: sort() expects parameter 1 to be array, object given in /Users/thomas/develop/php-src/mytest.php on line 6

Call Stack:
    0.0010     226384   1. {main}() /Users/thomas/develop/php-src/mytest.php:0
    0.0030     228384   2. sort() /Users/thomas/develop/php-src/mytest.php:6

class ArrayObject#1 (1) {
  private $storage =>
  array(3) {
    [0] =>
    int(3)
    [1] =>
    int(2)
    [2] =>
    int(1)
  }
}