Switch to UTF-8

[julmud]

Everything is set to use the charset windows-1252 (from the database, to the web pages served, including the source code and translations).

This forces charset conversions in some places in the code. For example, in functions.php we find:

function strftimeReplacement(string $format, ?int $timestamp = null)
{
	global $lang;
	return mb_convert_encoding(strftime($format, $timestamp, $lang['__strftime_locale']), 'WINDOWS-1252', 'UTF-8');
}

Making everything being UTF-8 would be a good choice going forward.

Watch out: the XML file generated by DVD Profiler would still be windows-1252, so we'd have to do some conversion when reading the XML file.