[PATCH] build-aux/txt2pre: drop CGI.pm requirement

[Eric Wong <e@80x24.org>]

CGI.pm is no longer in the main Perl distro, so depending
on it is not worth the effort for a few lines.
---
 build-aux/txt2pre | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/build-aux/txt2pre b/build-aux/txt2pre
index d1eadc6..276728f 100755
--- a/build-aux/txt2pre
+++ b/build-aux/txt2pre
@@ -7,7 +7,6 @@
 # and requires indentation to output preformatted text.
 use strict;
 use warnings;
-use CGI qw/escapeHTML/;
 use Encode qw/encode/;
 my $file = shift;
 my $str;
@@ -18,8 +17,14 @@ if (defined $file) {
 } else {
 	$str = eval { local $/; <> };
 }
-
-$str = escapeHTML($str);
+my %xhtml_map = (
+	'"' => '&#34;',
+	'&' => '&#38;',
+	"'" => '&#39;',
+	'<' => '&lt;',
+	'>' => '&gt;',
+);
+$str =~ s/([<>&'"])/$xhtml_map{$1}/ge;
 $str = encode('us-ascii', $str, Encode::HTMLCREF);
 my ($title) = ($str =~ /\A([^\n]+)\n[^a-zA-Z]*\n/s);