Fix axes bounding box not obeying 'layer' property. * gl-render.cc (draw_axes_boxes): Check layer2Dtop to decide which Z-value to place axis at. In 2-D plot, don't draw box lines at second Z-value which overlaps original axis and is always on top. * graphics.cc (update_axes_layout): Set property is2D based on whether view() elevation is 90 degrees. * graphics.in.h (axes::properties): New is2D bool property. * graphics.in.h (axes::properties::get_is2D): New getter function.

--- a/libinterp/corefcn/graphics.cc	Wed Apr 23 11:01:30 2014 -0700
+++ b/libinterp/corefcn/graphics.cc	Wed Apr 23 18:48:30 2014 -0700
@@ -5199,6 +5199,7 @@
 
   Matrix viewmat = get_view ().matrix_value ();
   nearhoriz = std::abs (viewmat(1)) <= 5;
+  is2D = viewmat(1) == 90;
 
   update_ticklength ();
 }