WP-Syntax

I modified your code so it accept ranges as well as single lines (ex: highlight="3,7,12-32,36"):

//START LINE HIGHLIGHT SUPPORT
$highlight = array();
if ( !empty($match[4]) )
{
    $highlight = strpos($match[4],',') == false ? array($match[4]) : explode(',', $match[4]);

    $h_lines = array();
    for($i = 0; $i < sizeof($highlight); $i++)
    {
        $h_range = explode('-', $highlight[$i]);

        if(sizeof($h_range) == 2)
        {
            $h_lines = array_merge($h_lines, range($h_range[0], $h_range[1]));
        }
        else
        {
           array_push($h_lines, $highlight[$i]);
        }
    }

    $geshi->highlight_lines_extra( $h_lines );
}
//END LINE HIGHLIGHT SUPPORT

Of course, the regex needs to be changed so it accepts dashes:

function wp_syntax_before_filter($content)
{
    return preg_replace_callback(
        "/\s*<pre(?:lang=[\"']([\w-]+)[\"']|line=[\"'](\d*)[\"']|escaped=[\"'](true|false)?[\"']|highlight=[\"']((?:\d+[,-])*\d+)[\"']|\s)+>(.*)<\/pre>\s*/siU",
        "wp_syntax_substitute",
        $content
    );
}