gitweb: Use underscore instead of hyphen to separate words in HTTP headers names

Use underscore (which will be turned into hyphen) to separate words in
HTTP header names, in keys to CGI header() method, consistently.
Signed-off-by: NJakub Narebski <jnareb@gmail.com>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

gitweb/gitweb.perl

@@ -2198,7 +2198,8 @@ sub git_blob_plain {
 		$save_as .= '.txt';
 	}
 
-	print $cgi->header(-type => "$type", '-content-disposition' => "inline; filename=\"$save_as\"");
+	print $cgi->header(-type => "$type",
+	                   -content_disposition => "inline; filename=\"$save_as\"");
 	undef $/;
 	binmode STDOUT, ':raw';
 	print <$fd>;
@@ -2382,8 +2383,8 @@ sub git_snapshot {
 	my $filename = basename($project) . "-$hash.tar.$suffix";
 
 	print $cgi->header(-type => 'application/x-tar',
-	                   -content-encoding => $ctype,
-	                  '-content-disposition' => "inline; filename=\"$filename\"",
+	                   -content_encoding => $ctype,
+	                   -content_disposition => "inline; filename=\"$filename\"",
 	                   -status => '200 OK');
 
 	open my $fd, "-|", "$GIT tar-tree $hash \'$project\' | $command" or
@@ -2701,7 +2702,7 @@ sub git_commitdiff_plain {
 
 	print $cgi->header(-type => "text/plain",
 	                   -charset => 'utf-8',
-	                  '-content-disposition' => "inline; filename=\"git-$hash.patch\"");
+	                   -content_disposition => "inline; filename=\"git-$hash.patch\"");
 	my %ad = parse_date($co{'author_epoch'}, $co{'author_tz'});
 	my $comment = $co{'comment'};
 	print "From: $co{'author'}\n" .