imagemagick: security bump to version 7.0.4-6
Fixes an use of uninitialized data issue in MAT image format that may have
security impact:
https://github.com/ImageMagick/ImageMagick/issues/362
[Peter: extend commit message, mention (potential) security impact]
Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit e5f505efac725b7e12b22f1341ce0523df73a79f)