Univention Corporate Server 4.2 erratum 561 (extended maintenance)

This update addresses the following issues:
* crash via malformed cpio archive (CVE-2015-8915)
* stack based buffer overflow in bsdtar_expand_char (util.c) (CVE-2016-8687)
* heap based buffer overflow in detect_form
  (archive_read_support_format_mtree.c) (CVE-2016-8688)
* heap based buffer overflow in read_header
  (archive_read_support_format_7zip.c) (CVE-2016-8689)
* NULL pointer dereference in archive_wstring_append_from_mbs function
  (CVE-2016-10209)
* Heap-based buffer over-read in the archive_le32dec function
  (CVE-2016-10349)
* Heap-based buffer over-read in the archive_read_format_cab_read_header
  function (CVE-2016-10350)
* Out of bounds read in lha_read_file_header_1() function (CVE-2017-5601)
* Heap-based buffer over-read in the atol8 function (CVE-2017-14166)
* Out-of-bounds read in parse_file_info (CVE-2017-14501)
* Off-by-one error in the read_header function (CVE-2017-14502)
* Out-of-bounds read in lha_read_data_none (CVE-2017-14503)