Since we're now using UTF-8 encoding everywhere, we need to convert any text that has been saved to the database in any other encoding. For iso-8859-1, we can use PHP's utf8_encode(), but for all other encodings, we need iconv or mbstring support in PHP. The upgrade script will check if any of these are available and if they are, run the conversion. If we can't reliably convert the text from PHP, the upgrade script will give clear instructions on how to do the conversion "manually".
As an added "bonus", we'll do our best to convert any HTML numeric character references that we encounter into their corresponding UTF-8 characters.
