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