Udating PHPMailer to version 5.2.3.

There is a bug in 5.2.2 occurring on some systems (including mine).

see [Issue 134: Warning: preg_match()](https://code.google.com/a/apache-extras.org/p/phpmailer/issues/detail?id=140&can=1&start=100)

Note: This PHPMailer version is [faulty marked as 5.2.2](https://code.google.com/a/apache-extras.org/p/phpmailer/source/browse/tags/5.2.3/class.phpmailer.php)