Update to XQuartz 2.7.6

Apple released XQuartz 2.7.6 on 2014.05.17. In addition to updating
several library dependencies XQuartz 2.7.6 addresses several CVE's
the worst of which may allow remote attackers to cause a denial of
service (crash) and possibly execute arbitrary code.

CVE's

- CVE-2014-2240
- CVE-2013-6462
- CVE-2014-0209
- CVE-2014-0210
- CVE-2014-0211