imagemagick - security update

This updates fixes several vulnerabilities in imagemagick: Various memory
handling problems and cases of missing or incomplete input sanitising
may result in denial of service or the execution of arbitrary code if
malformed SIXEL, PDB, MAP, SGI, TIFF and CALS files are processed.

For the stable distribution (jessie), these problems have been fixed in
version 8:6.8.9.9-5+deb8u5.

For the unstable distribution (sid), these problems will be fixed soon.

We recommend that you upgrade your imagemagick packages.