Added support for foreach with list statement (PHP 5.5)

Currently, pdepend does not support to analyze codes which uses [foreach with list](http://php.net/manual/de/migration55.new-features.php#migration55.new-features.foreach-list) (which was introduced in PHP 5.5)

```
$array = [
    [1, 2],
    [3, 4],
];

foreach ($array as list($a, $b)) {
    echo "A: $a; B: $b\n";
}
```

Before, this code led to the following error: `Unexpected token: list, line: 8, col: 18, file: /../foreachlist.php`