MFH: r456538

Update to 1.1.15

This update contains a fix for CVE-2017-16612, integer overflow that can
lead to a heap buffer overflow when parsing malicious files.

For general changelog, see
https://lists.x.org/archives/xorg-announce/2017-November/002823.html

Security: ddecde18-e33b-11e7-a293-54e1ad3d6335

Approved by: ports-secteam (delphij)