Don't use explicit figure number for tests to avoid interference with any figures opened by user. (plot/allchild.m, plot/ancestor.m, plot/cla.m, plot/clf.m, plot/close.m, plot/findall.m, plot/findobj.m, plot/gca.m, plot/gcf.m, plot/hggroup.m, plot/isfigure.m, plot/line.m, plot/loglog.m, plot/patch.m, plot/semilogx.m, plot/semilogy.m, plot/surface.m, plot/view.m, plot/whitebg.m, plot/xlim.m, plot/ylim.m, plot/zlim.m): Don't use explicit figure numer 1232 any more.

--- a/scripts/plot/isfigure.m
+++ b/scripts/plot/isfigure.m
@@ -36,10 +36,10 @@
 endfunction
 
 %!test
-%! hf = figure (1232, "visible", "off");
+%! hf = figure ("visible", "off");
 %! unwind_protect  
-%!   assert (isfigure (1232));
-%!   assert (!isfigure (-1232));
+%!   assert (isfigure (hf));
+%!   assert (!isfigure (-hf));
 %! unwind_protect_cleanup
 %!   close (hf);
 %! end_unwind_protect