* develop-olympus:
[ticket/9609] Change header() calls setting HTTP status to send_status_line().
[ticket/9613] Slightly update language strings.
[ticket/9613] Fix missing database part for unread posts search load switch.
[ticket/9613] Implement a load switch for unread posts search feature.
[ticket/9785] Allow users to request new passwords when board is disabled.
[ticket/9644] Check $mode before calling user_notification() from submit_post()