Updated libxml2 packages fix security vulnerability

Integer overflow in memory debug code in libxml2 before 2.9.5 (CVE-2017-5130). It was discovered that libxml2 incorrecty handled certain files. An attacker could use this issue with specially constructed XML data to cause libxml2 to consume resources, leading to a denial of service (CVE-2017-15412). Wei Lei discovered that libxml2 incorrecty handled certain parameter entities. An attacker could use this issue with specially constructed XML data to cause libxml2 to consume resources, leading to a denial of service (CVE-2017-16932). The libxml2 package has been updated to version 2.9.7 to fix these issues and several other bugs. Also, the perl-XML-LibXML package has been updated to version 2.13.200 to allow it to be rebuilt against the updated libxml2.