Fix Z-order stacking of patches and axes grid lines (bug #40722). * gl-render.h (set_polygon_offset): Change function prototype for offset argument to float. * gl-render.cc (set_polygon_offset): Change offset argument to type float. Now matches OpenGL prototype for glPolygonOffset. * gl-render.cc (patch_tesselator::patch_tesselator): Change constructor variable idx to a float, from int. * gl-render.cc (patch_tesselator::begin): Pass index directly to set_polygon_offset. * gl-render.cc (opengl_renderer::draw_patch): Call patch_tesselator with index of 1.0 for filled portion of patch to push it down below outline of patch. * patch.m: For 2-D patches, set zlim to [-1,1] so that axes 'layer' property works.

% Increase save size to run @seealso macro for Octave documentation
save_size = 10000