Add further tests for scripts/plot. plot/close.m: Tests added. plot/gca.m, plot/gcbf.m, plot/gcbo.m, plot/hggroup.m, plot/isfigure.m: Ditto. plot/gtext.m, plot/ginput.m: Dummy test added.

--- a/scripts/plot/ginput.m
+++ b/scripts/plot/ginput.m
@@ -42,3 +42,7 @@
   endif
 
 endfunction
+
+## Remove from test statistics.  No real tests possible.
+%!test
+%! assert (1);