use ' instead of ` in error messages, warnings and most comments * intro.txi, io.txi, munge-texi.cc, octave.texi, cmd-edit.cc, data-conv.cc, file-ops.cc, glob-match.h, kpse.cc, oct-env.cc, oct-locbuf.h, oct-md5.cc, oct-rand.cc, general/interp2.m, doc.m, get_first_help_sentence.m, help.m, print_usage.m, __additional_help_message__.m, type.m, unimplemented.m, which.m, cast.m, dir.m, license.m, mkoctfile.m, recycle.m, tempdir.m, optimset.m, pkg/pkg.m, closereq.m, colstyle.m, __fltk_print__.m, __gnuplot_print__.m, __go_draw_figure__.m, __pie__.m, __pltopt__.m, __print_parse_opts__.m, uigetdir.m, uigetfile.m, uiputfile.m, stft.m, mean.m, anova.m, cor_test.m, t_test_regression.m, __magick_read__.cc, dlmread.cc, schur.cc, data.cc, debug.cc, defun-dld.h, defun.cc, defun.h, dynamic-ld.cc, error.cc, error.h, gl-render.cc, graphics.cc, gripes.cc, input.cc, lex.ll, load-path.cc, load-save.cc, ls-hdf5.cc, ls-mat-ascii.cc, ls-mat4.cc, ls-mat5.cc, ls-oct-ascii.cc, ls-oct-binary.cc, oct-hist.cc, oct-parse.yy, oct-stream.cc, oct-stream.h, octave.cc, ov-base-diag.cc, ov-base.cc, ov-class.cc, ov-colon.h, ov-struct.cc, ov-typeinfo.cc, ov.cc, pager.cc, pr-output.cc, pt-binop.cc, pt-eval.cc, pt-id.cc, pt-idx.cc, pt-misc.cc, pt-unop.cc, symtab.cc, symtab.h, toplev.cc, txt-eng-ft.cc, utils.cc, variables.cc, test_eval-catch.m, test_try.m: Use ' instead of ` in error messages, warnings, and most comments.

--- a/src/gripes.cc
+++ b/src/gripes.cc
@@ -103,7 +103,7 @@
 void
 gripe_invalid_value_specified (const char *name)
 {
-  warning ("invalid value specified for `%s'", name);
+  warning ("invalid value specified for '%s'", name);
 }
 
 void
@@ -134,9 +134,9 @@
 gripe_wrong_type_arg (const char *name, const char *s, bool is_error)
 {
   if (is_error)
-    error ("%s: wrong type argument `%s'", name, s);
+    error ("%s: wrong type argument '%s'", name, s);
   else
-    warning ("%s: wrong type argument `%s'", name, s);
+    warning ("%s: wrong type argument '%s'", name, s);
 }
 
 void
@@ -165,14 +165,14 @@
 gripe_wrong_type_arg_for_unary_op (const octave_value& op)
 {
   std::string type = op.type_name ();
-  error ("invalid operand `%s' for unary operator", type.c_str ());
+  error ("invalid operand '%s' for unary operator", type.c_str ());
 }
 
 void
 gripe_wrong_type_arg_for_binary_op (const octave_value& op)
 {
   std::string type = op.type_name ();
-  error ("invalid operand `%s' for binary operator", type.c_str ());
+  error ("invalid operand '%s' for binary operator", type.c_str ());
 }
 
 void