Package libImageMagick: Information

- backport to 7

- Apply security patches from Debian:
  ImageTragick: The coders EPHEMERAL, URL, HTTPS, MVG, MSL, TEXT,
  SHOW, WIN, and PLT are disabled via policy.xml file, since they are
  vulnerable to code injection. This mitigates CVE-2016-3714,
  CVE-2016-3715, CVE-2016-3716, CVE-2016-3717, and CVE-2016-3718.
  Since ImageMagick reverts to its internal SVG renderer (which uses
  MVG coder) if Inkscape or RSVG is not used, the option --with-rsvg
  is included. Closes: 823542. In addition, some other actions were
  taken with respect to these vulnerabilities:
  - Drop the PLT/Gnuplot decoder, which was vulnerable to command
  injection.
  - Some sanitization for input filenames in http/https delegates is
  added.
  - Indirect filename are now authorized by policy.
  - Indirect reads with label:@ are prevented.
  - Less secure coders (such as MVG, TEXT, and MSL) require explicit
    reference in the filename (e.g. mvg:my-graph.mvg).

- Avoid ImageMagick pipe i/o bug