RFC2231 attachments files names fixes
[fixed] Original file name in IncomingMailAttachment::$name
[fixed] Parameter value continuations is now supported. See http://tools.ietf.org/html/rfc2231#section-3 (thanks to troggy)
[fixed] Parameter value extended encoding is now supported. See http://tools.ietf.org/html/rfc2231#section-4 (thanks to troggy)