New plot style pm3d

The splot command is now capable of plotting 2D maps and 3D surfaces colored by greyscale or color palettes. See help for set pm3d (p. ), set palette (p. ), set cbrange (p. ), set view map (p. ), set colorbox (p. ) and test palette (p. ).

Sample scripts: pm3d.dem pm3dcolors.dem pm3dgamma.dem