Univention Corporate Server 4.1 erratum 488 (extended maintenance)

This update addresses the following issues:
* A remote code execution vulnerability in libxml2 could enable an attacker
  using a specially crafted file to execute arbitrary code within the
  context of an unprivileged process. This issue is rated as High due to
  the possibility of remote code execution in an application that uses this
  library (CVE-2017-0663)
* heap overflow in memory debug code (CVE-2017-5130)
* Missing validation for external entities in xmlParsePEReference
  (CVE-2017-7375)
* Incorrect limit used for port values (CVE-2017-7376)
* Denial of Service (application crash) due to buffer overflow in function
  xmlSnprintfElementContent in valid.c (CVE-2017-9047)
* Denial of Service (application crash) due to stack-based buffer overflow
  in the function xmlSnprintfElementContent in valid.c (CVE-2017-9048)
* Denial of Service (application crash) due to heap-based buffer over-read
  in the xmlDictComputeFastKey function in dict.c (CVE-2017-9049)
* Denial of Service (application crash) due to heap-based buffer over-read
  in the xmlDictAddString function in dict.c (CVE-2017-9050)
* parser.c mishandles parameter-entity references because the NEXTL macro
  calls the xmlParserHandlePEReference function in the case of a '%'
  character in a DTD name (CVE-2017-16931)
* parser.c does not prevent infinite recursion in parameter entities
  (CVE-2017-16932)