Bug 13815 - plack loose CGI qw(-utf8) flag creating incorrect utf-8 encoding everywhere

Bug 13815 - plack loose CGI qw(-utf8) flag creating incorrect utf-8 encoding everywhere

This is major problem for plack installations with utf-8 encoding.

In this case, we are overriding CGI->new to setup utf-8 flag and
get correctly decoded $cgi->params, and reset syspref cache using
C4::Context->clear_syspref_cache

Test scenario:
1. under plack try to search with utf-8 charactes
2. try to find patron with utf-8 characters

Signed-off-by: Gaetan Boisson <gaetan.boisson@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>