ghostscript vulnerability

USN-5396-1 addressed a vulnerability in Ghostscript. This update
provides the corresponding update for Ubuntu 16.04 ESM.

Original advisory details:

It was discovered that Ghostscript incorrectly handled certain PostScript
files. If a user or automated system were tricked into processing a
specially crafted file, a remote attacker could possibly use this issue to
access arbitrary files, execute arbitrary code, or cause a denial of
service.