imagemagick: bump to version 6.8.8-7

Signed-off-by: Jerzy Grzegorek <jerzy.grzegorek@trzebnica.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/imagemagick/imagemagick.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-IMAGEMAGICK_VERSION = 6.8.8-4
+IMAGEMAGICK_VERSION = 6.8.8-7
 IMAGEMAGICK_SOURCE = ImageMagick-$(IMAGEMAGICK_VERSION).tar.xz
 # The official ImageMagick site only keeps the latest versions
 # available, which is annoying. Use an alternate site that keeps all