Update imagemagick entry

• Fix indention
• Add ranges to the imagemagick 6 version check, to prep for ImageMagick patch for the branch.
• Add portepoch's to the imagemagick 6 versions.
• Bump imagemagick 6 version. This version fixes at least one of the mentioned CVE's.
• Change CVE-2017-8365 to CVE-2017-8765. CVE-2017-8365 is a libsndfile CVE.
• Add modified tag.