This set:
sci-mathematics/octave-5.1.0
media-gfx/imagemagick-7.0.9.16
doesn't work: requires a fix that imagemagick is found in the first place,
but if found by configure, later fails building.
So this switches it to use graphicsmagick instead.
(Sabayon bug 5883.)
Sławomir Nizio
dad4055e7e