* src/engine/rfc822/rfc822-mailbox-address.vala (MailboxAddress): Escape
  and encode name and mailbox (local-part) when serialising as a RFC 822
  string. Provide a means to get a RFC 822 version of the address only
  for SMTP. Add unit tests.

* src/engine/smtp/smtp-request.vala (MailRequest): Use proper RFC 822
  formatted version of mailbox addresses.