Only postscript terminals were excluded from the colorbox rendering changes introduced in Patch #785. The reason is that the colorbox rendering routine for postscript terminals (draw_inside_color_smooth_box_postscript) was implemented separately from the other terminals.
In this patch, the same drawing routine is used for discrete gradient palettes as for other terminals, even for postscript terminals. For smooth gradient palettes (and mixed gradient palettes), the optimized drawing routines are used as before.
The maxcolors setting is disabled in the output postscript file because it is meaningless for the discrete gradient palette to limit the colors by maxcolors. This behavior is the same for other terminals.
