libgd2 - security update

• CVE-2016-6911
  invalid read in gdImageCreateFromTiffPtr()
  (most of the code is not present in the Wheezy version)
• CVE-2016-8670
  Stack Buffer Overflow in GD dynamicGetbuf

For Debian 7 Wheezy, these problems have been fixed in version
2.0.36~rc1~dfsg-6.1+deb7u6.

We recommend that you upgrade your libgd2 packages.

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: <https://wiki.debian.org/LTS&gt;