Description:
------------
Exception's stacktraces miss the "args" key in certain situations (whereas debug_backtrace() will report them).

Reproduce code:
---------------
php -r 'class Chained extends Exception { function __construct($message, $cause) { parent::__construct($message); $this->cause= $cause; }} function raise($message, $cause) { throw new Chained($message, new Exception($cause)); } try { raise("Arg", "Cause"); } catch (Exception $e) { var_dump($e->getTrace(), $e->cause->getTrace()); }'

Expected result:
----------------
Twice this:

array(1) {
  [0]=>
  array(4) {
    ["file"]=>
    string(17) "Command line code"
    ["line"]=>
    int(1)
    ["function"]=>
    string(5) "raise"
    ["args"]=>
    array(2) {
      [0]=>
      &string(3) "Arg"
      [1]=>
      &string(5) "Cause"
    }
  }
}


Actual result:
--------------
array(1) {
  [0]=>
  array(4) {
    ["file"]=>
    string(17) "Command line code"
    ["line"]=>
    int(1)
    ["function"]=>
    string(5) "raise"
    ["args"]=>
    array(2) {
      [0]=>
      string(3) "Arg"
      [1]=>
      string(5) "Cause"
    }
  }
}
array(1) {
  [0]=>
  array(3) {
    ["file"]=>
    string(17) "Command line code"
    ["line"]=>
    int(1)
    ["function"]=>
    string(5) "raise"
  }
}

The second array is missing the "args" key. In PHP 5.3, it's present.