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/symtab.cc	Sun Sep 23 10:36:25 2012 -0700
+++ b/src/symtab.cc	Mon Oct 01 17:18:49 2012 -0400
@@ -1658,7 +1658,7 @@
           retval = symbol_table::varval (name);
 
           if (retval.is_undefined ())
-            error ("variable_value: `%s' is not a variable in the current scope",
+            error ("variable_value: '%s' is not a variable in the current scope",
                    name.c_str ());
         }
       else