Security update for roundcubemail (important)

This update for roundcubemail fixes the following issues:

  - A maliciously crafted email could cause untrusted code to be executed
    (cross site scripting using $lt;area href=javascript:...>)
    (boo#982003, CVE-2016-5103)
  - Avoid HTML styles that could cause potential click jacking
    (boo#1001856)
  - A maliciously crafted FROM value could cause extra parameters to be
    passed to the sendmail command (boo#1012493)
  - Avoid sending completely empty text parts for multipart/alternative
    messages
  - Don't create multipart/alternative messages with empty text/plain part
  - Improved validation of FROM argument when sending mails