Bug 8953 - opac-userupdate encoding issues

Bug 8953 - opac-userupdate encoding issues

This script has various encoding problems:

1. parametars from CGI are not encoded in utf-8, so when they are
   compared with utf-8 strings from database every field with
   utf-8 characters will be reported in e-mail as changed
2. when sending e-mail, wide characters are passed to Mail::Sendmail
   which results in software error if edited field has utf-8 characters
   (because of first point, this happend if ANY fields has utf-8 chars)
3. when declaring encoding for outgoing e-mail utf-8 is more correct
   than just utf8

Test scenario:

1. open opac-userupdate and edit user which has utf-8 characters in
   at least one field (firstname and surname are common examples)
2. edit one of other fields and add utf-8 character to it
3. verify that e-mail with changes arrived with just edited field

Signed-off-by: Mirko Tietgen <mirko@abunchofthings.net>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>