libxml2 - security update

• CVE-2016-4658
  Namespace nodes must be copied to avoid use-after-free errors.
  But they don’t necessarily have a physical representation in a
  document, so simply disallow them in XPointer ranges.
• CVE-2016-5131
  The old code would invoke the broken xmlXPtrRangeToFunction.
  range-to isn’t really a function but a special kind of
  location step. Remove this function and always handle range-to
  in the XPath code.
  The old xmlXPtrRangeToFunction could also be abused to trigger
  a use-after-free error with the potential for remote code
  execution.

For Debian 7 Wheezy, these problems have been fixed in version
2.8.0+dfsg1-7+wheezy7.

We recommend that you upgrade your libxml2 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;