Problems with accented characters in feedback emails on some systems

[taniwallach]

See: https://webwork.maa.org/moodle/mod/forum/discuss.php?d=4916

It seems possible that the use of encode_utf8($msg) made in #973 will need to be replaced by the use of encode("UTF-8", $msg).

We need confirmation that this helps on systems experiencing such problems before making such a change.