Univention Corporate Server 4.2 erratum 580 (extended maintenance)

This update addresses the following issues:
* Buffer overflow in the flac_buffer_copy function (CVE-2017-8361)
* Out-of-bounds read in the flac_buffer_copy function (CVE-2017-8362)
* Heap buffer over-read in the flac_buffer_copy function (CVE-2017-8363)
* Buffer over-read in the l2les_array function (CVE-2017-8365)
* Out-of-bounds read in the function d2alaw_array() (CVE-2017-14245)
* Out-of-bounds read in the function d2ulaw_array() (CVE-2017-14246)
* Divide-by-zero in the double64_init() function (CVE-2017-14634)
* SEGV on unknown address in the function d2alaw_array() (CVE-2017-17456)
* SEGV on unknown address in the function d2ulaw_array() (CVE-2017-17457)
* stack-based buffer overflow in sndfile-deinterleave utility
  (CVE-2018-13139)
* OOB read in sf_write_int in sndfile.c (CVE-2018-19432)
* buffer over-read in the function i2ulaw_array in ulaw.c (CVE-2018-19661)
* buffer over-read in the function i2alaw_array in alaw.c (CVE-2018-19662)