Description of PHPMailer 1.73 library import into Moodle

Changes:

class.phpmailer.php
 * Duplicate Message-IDs in Forum mail (MDL-3681)
 * Support for gb18030 (MDL-5229)
 * Correct timezone in date (MDL-12596)
 * Backported fixes for CVE-2007-3215 (MDL-18348)
