Fix rare PclZip/realpath/PHP version problem

In PHP 5.4.4 `realpath()` handles absolute paths correctly, but in PHP 5.3.8 returns false.

Note: PHP 5.4.4 and PHP 5.3.8 on Windows.

```php
// PHP 5.4.4 - pass - returns original path
// PHP 5.3.8 - fail - returns false
$tempfile = tempnam(sys_get_temp_dir(), "PHPWORD");

echo realpath($tempfile);
```