sci-mathematics/octave-4.4.0: Fix build with media-gfx/graphicsmagick…

…-1.3.30[imagemagick]

With USE="graphicsmagick imagemagick", the build would previously fail with:
```
libinterp/corefcn/__magick_read__.cc:801:11: error: ‘MAGICKCORE_QUANTUM_DEPTH’ was not declared in this scope
```

Closes: https://bugs.gentoo.org/661046

sci-mathematics/octave/files/octave-4.4.0-imagemagick.patch

@@ -1,16 +1,22 @@
 --- a/libinterp/corefcn/__magick_read__.cc	2018-05-22 12:25:37.688173855 +0200
 +++ a/libinterp/corefcn/__magick_read__.cc.new	2018-05-22 12:32:51.475172200 +0200
-@@ -817,10 +817,11 @@
+@@ -817,10 +817,19 @@
        // depth is 8, there's a good chance that we will be limited.  It
        // is also the GraphicsMagick recommended setting and the default
        // for ImageMagick.
--      if (QuantumDepth < 16)
++#ifdef QuantumDepth
+       if (QuantumDepth < 16)
++#else
 +      using namespace Magick;
 +      if (MAGICKCORE_QUANTUM_DEPTH < 16)
++#endif
          warning_with_id ("Octave:GraphicsMagick-Quantum-Depth",
                           "your version of %s limits images to %d bits per pixel\n",
--                         MagickPackageName, QuantumDepth);
++#ifdef QuantumDepth
+                          MagickPackageName, QuantumDepth);
++#else
 +                         MagickPackageName, MAGICKCORE_QUANTUM_DEPTH);
++#endif
 
        initialized = true;
      }