imagemagick: update patchset from 9 to 10

The ImageMagick-6.9.1-9.tar.xz is gone again.

To avoid somebody doing the same mistake as I did - updating to an unfinished
series - a note was dropped. Hopefully we don't see too many further patchsets
within this version...

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>