USN-5778-2: X.Org X Server vulnerabilities

USN-5778-1 fixed several vulnerabilities in X.Org. This update provides
the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.

Original advisory details:

Jan-Niklas Sohn discovered that X.Org X Server extensions contained
multiple security issues. An attacker could possibly use these issues to
cause the X Server to crash, execute arbitrary code, or escalate
privileges.

advisory code crash extensions org privileges security security issues server ubuntu update usn vulnerabilities x.org