gitweb: Convert generated contents to utf8 in commitdiff_plain

If the commit message, or commit author contains non-ascii, it must be
converted from Perl internal representation to utf-8, to follow what
got declared in HTTP header.  Use to_utf8() to do the conversion.

This necessarily replaces here-doc with "print" statements.
Signed-off-by: NYasushi SHOJI <yashi@atmark-techno.com>
Acked-by: Nİsmail Dönmez <ismail@pardus.org.tr>
Acked-by: NJakub Narebski <jnareb@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -5048,16 +5048,15 @@ sub git_commitdiff {
 			-expires => $expires,
 			-content_disposition => 'inline; filename="' . "$filename" . '"');
 		my %ad = parse_date($co{'author_epoch'}, $co{'author_tz'});
-		print <<TEXT;
-From: $co{'author'}
-Date: $ad{'rfc2822'} ($ad{'tz_local'})
-Subject: $co{'title'}
-TEXT
+		print "From: " . to_utf8($co{'author'}) . "\n";
+		print "Date: $ad{'rfc2822'} ($ad{'tz_local'})\n";
+		print "Subject: " . to_utf8($co{'title'}) . "\n";
+
 		print "X-Git-Tag: $tagname\n" if $tagname;
 		print "X-Git-Url: " . $cgi->self_url() . "\n\n";
 
 		foreach my $line (@{$co{'comment'}}) {
-			print "$line\n";
+			print to_utf8($line) . "\n";
 		}
 		print "---\n\n";
 	}