Multicolor mesh plot patch

I'm not sure which list is best for this, so I'm sending it to bug and 
graphics. Someone recently was complaining about the quality of mesh 
plots, and I agree the two-color plots don't look that great. I 
discovered that this can be changed quite easily using gnuplot 4.0 
features. The attached patch makes mesh use color lines. It also defines 
a color palette that is very similar to Matlab's default palette. I 
don't know if this is the best way to do this, I'm open to suggestions 
on how to improve it. One thing that's missing is a check for whether 
the "palette" line type is valid. The octave-forge functions surf and 
surfc use a global gnuplot_has_pm3d, but it's a bit of a hack and I 
doubt John wants stuff like this in core Octave code. Is there any way 
to verify the capabilities of gnuplot from octave? We have things like 
OCTAVE_VERSION and OCTAVE_FORGE_VERSION defined, would it make sense to 
define GNUPLOT_VERSION?

-Quentin

Index: mesh.m
===================================================================
RCS file: /cvs/octave/scripts/plot/mesh.m,v
retrieving revision 1.31
diff -u -r1.31 mesh.m
--- a/mesh.m    15 Jun 2005 03:49:23 -0000      1.31
+++ b/mesh.m    26 Sep 2005 20:54:59 -0000
@@ -75,7 +75,10 @@
         __gnuplot_raw__ ("set nologscale;\n");
         __gnuplot_set__ parametric;
         __gnuplot_raw__ ("set view 60, 30, 1, 1;\n");
-        __gnuplot_splot__ (zz);
+        __gnuplot_set__ palette defined ( 0 "dark-blue", 1 "blue", ...
+                  2 "cyan", 3 "yellow", 4 "red" , 5 "dark-red" )
+        __gnuplot_set__ nocolorbox
+        __gnuplot_splot__ zz with line palette;
         __gnuplot_set__ noparametric;
       else
         msg = "mesh: rows (z) must be the same as length (y) and";