USN-4905-2: X.Org X Server vulnerability

USN-4905-1 fixed a vulnerability in X.Org. This update provides the corresponding update for Ubuntu 14.04 ESM. Original advisory details: Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled certain lengths of XInput extension ChangeFeedbackControl requests. An attacker could use this issue to cause the server to crash, resulting in a denial of service, or possibly execute arbitrary code.