MFH: r418585

graphics/tiff: Patch vulnerabilities

These two patches were obtained from OpenBSD. An additional CVE is not
yet addressed, but upstream indicates they are removing the gif2tiff
utility as the mitigation in the upcoming 4.0.7.

PR: 211113
Security: CVE-2016-5875
Security: CVE-2016-3186

Approved by: ports-secteam (with hat)