LdapUrl: fix LDAP queries broken with non-ascii search strings.
Summary: Qt5 made query() return a PrettyDecoded query string, while the code was calling fromPercentEncoding for the filter, i.e. assuming it to be FullyEncoded. With unittest Test Plan: Typing Valérie in kmail composer now finds LDAP completion correctly. Reviewers: dvratil, mlaurent Reviewed By: dvratil Subscribers: #kde_pim Tags: #kde_pim Differential Revision: https://phabricator.kde.org/D12387