Univention Corporate Server 4.2 erratum 455 (security)

This update addresses the following issues:
* Out-of-bounds heap read in mng_get_long function (CVE-2017-10995)
* Heap-buffer over-read in the WriteUILImage() function (CVE-2017-11533)
* Heap-based buffer over-read in the WritePSImage() function (CVE-2017-11535)
* heap-based buffer over-read in the WriteCIPImage() function in coders/cip.c
  (CVE-2017-11639)
* Initialized data use in ReadMATImage function in coders/mat.c
  (CVE-2017-13143)
* Heap-based buffer overflow in Magick_png_read_raw_profile (CVE-2017-17504)
* Heap-based buffer over-read in ReadOneMNGImage function in coders/png.c
  (CVE-2017-17879)
* Heap-based buffer over-read in the ReadSIXELImage function in
  coders/sixel.c (CVE-2018-5248)
* heap-based buffer over-read in ReadSUNImage in coders/sun.c
  (CVE-2018-11251)
* out of bounds write in ReadBMPImage and WriteBMPImage in coders/bmp.c
  (CVE-2018-12599)
* out of bounds write ReadDIBImage and WriteDIBImage in coders/dib.c
  (CVE-2018-12600)