bad HTML message display

Hi,

  I've noticed that when displaying an HML message with a charset
different than sqwebmail one's (utf-8 in my case), non ascii
characters are not converted, so they are badly rendered. It work fine
when the message is a multipart/alternative and the "Display HTML
E-Mail" preference is off.

  I've looked in folder.c to try a patch, but theyre is a big stack of
filters, so it's uneasy for me to make a clean fix.