Fix a bug while interpreting an exception list.
Use ArrayIterator instead of ArrayObject.
New interfaces for the @throwable clause.

The @throwable clause implements IteratorAggregate and Countable.
New @throwable clause API.
Add a weak stack.

A weak stack is a stack where null elements are not iterated. Example:

    $stack = new WeakStack();
    $stack->push(2);
    $stack->push(null);
    $stack->push(4);
    $stack->push(null);
    $stack->push(null);
    $stack->pop();

    foreach($stack as $element)
        var_dump($element);

    /**
     * Will output:
     *     int(4)
     *     int(2)
     */
Take @throwable into account when iterating.
[auto] Merge from Praspel

    • #06af2a4 — Fix a bug while interpreting an exception list. (Ivan Enderlin, 2013-04-23)
    • #3f09de1 — Use ArrayIterator instead of ArrayObject. (Ivan Enderlin, 2013-04-23)
    • #057439b — New interfaces for the @throwable clause. (Ivan Enderlin, 2013-04-23)
    • #73afcad — New @throwable clause API. (Ivan Enderlin, 2013-04-23)
    • #2af5ad6 — Add a weak stack. (Ivan Enderlin, 2013-04-23)
    • #59c0d3b — Take @throwable into account when iterating. (Ivan Enderlin, 2013-04-23)

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Merge remote branch 'library-praspel/master'