Remove nofollow attribute in wordpress links and text

functions.php

/**
 * Removes the value ›nofollow‹ from the rel attribute.
 */
function xwp_dofollow($str)
{
    $str = preg_replace(
        '~<a ([^>]*)\s*(["|\']{1}\w*)\s*nofollow([^>]*)>~U',
        '<a ${1}${2}${3}>', $str);
    return str_replace(array(' rel=""', " rel=''"), '', $str);
}
remove_filter('pre_comment_content',     'wp_rel_nofollow');
add_filter   ('get_comment_author_link', 'xwp_dofollow');
add_filter   ('post_comments_link',      'xwp_dofollow');
add_filter   ('comment_reply_link',      'xwp_dofollow');
add_filter   ('comment_text',            'xwp_dofollow');