Univention Corporate Server 4.4 erratum 388 (security)

This update addresses the following issues:
* Arbitrary path overwriting via export-marks command option (CVE-2019-1348)
* Recursive submodule cloning allows using git directory twice with
  synonymous directory name written in .git/ (CVE-2019-1349)
* Files inside the .git directory may be overwritten during cloning via NTFS
  Alternate Data Streams (CVE-2019-1352)
* NTFS protections inactive when running Git in the Windows Subsystem for
  Linux (CVE-2019-1353)
* Remote code execution in recursive clones (CVE-2019-1387)