maint: Remove unneeded input validation from internal fcns in private/ directories. * scripts/general/private/__isequal__.m, scripts/general/private/__splinen__.m, scripts/image/private/__imwrite__.m, scripts/image/private/ind2x.m, scripts/miscellaneous/private/__xzip__.m, scripts/miscellaneous/private/display_info_file.m, scripts/pkg/private/describe.m, scripts/pkg/private/get_forge_pkg.m, scripts/pkg/private/unload_packages.m, scripts/plot/private/__actual_axis_position__.m, scripts/plot/private/__add_datasource__.m, scripts/plot/private/__clabel__.m, scripts/plot/private/__errcomm__.m, scripts/plot/private/__errplot__.m, scripts/plot/private/__fltk_print__.m, scripts/plot/private/__gnuplot_get_var__.m, scripts/plot/private/__go_draw_axes__.m, scripts/plot/private/__go_draw_figure__.m, scripts/plot/private/__interp_cube__.m, scripts/plot/private/__line__.m, scripts/plot/private/__next_line_color__.m, scripts/plot/private/__next_line_style__.m, scripts/plot/private/__plt__.m, scripts/plot/private/__pltopt__.m, scripts/signal/private/rectangle_lw.m, scripts/signal/private/rectangle_sw.m, scripts/signal/private/triangle_lw.m, scripts/signal/private/triangle_sw.m, scripts/sparse/private/__sprand_impl__.m, scripts/statistics/models/private/logistic_regression_derivatives.m, scripts/statistics/models/private/logistic_regression_likelihood.m: Remove unneeded input validation from internal fcns in private/ directories.

--- a/scripts/plot/private/__fltk_print__.m
+++ b/scripts/plot/private/__fltk_print__.m
@@ -42,7 +42,7 @@
     case {"eps", "eps2", "epsc", "epsc2"}
       ## format GL2PS_EPS
       gl2ps_device = {"eps"};
-      ## FIXME - use epstool to tighten bbox and provide preview.
+      ## FIXME: use epstool to tighten bbox and provide preview.
       pipeline = {opts.epstool_cmd(opts, "-", opts.name)};
     case {"epslatex", "pslatex", "pdflatex", "epslatexstandalone", ...
           "pslatexstandalone", "pdflatexstandalone"}
@@ -67,7 +67,7 @@
       gl2ps_device = {sprintf("%snotxt", lower (suffix))};
       gl2ps_device{2} = "tex";
       if (dos_shell)
-        ## FIXME - this will only work on MinGW with the MSYS shell
+        ## FIXME: this will only work on MinGW with the MSYS shell
         pipeline = {sprintf("cat > %s-inc.%s", name, suffix)};
         pipeline{2} = sprintf ("cat > %s.tex", name);
       else