sci-mathematics/octave: new version 5.2.0 sans imagemagick support.

sci-mathematics/octave: new version 5.2.0 sans imagemagick support.

This new version drops two patches (zlib underlinking and qt-5.11
support) that have been fixed upstream in other ways. Unfortunately,
it also temporarily disables USE=imagemagick, because the upstream
support for imagemagick is broken. In the past, we have carried custom
patches to fix that, but they no longer apply, and upstream has hinted
that the approach they take will not be accepted. So to get this out
the door, the simplest thing to do is to follow upstream and throw
imagemagick under a bus.

Bug: https://bugs.gentoo.org/401189
Bug: https://bugs.gentoo.org/660298
Closes: https://bugs.gentoo.org/709388
Package-Manager: Portage-2.3.89, Repoman-2.3.20
Signed-off-by: Michael Orlitzky <mjo@gentoo.org>