imap-del-for-mh.php: Add dir to store error mh files in
imap-del-for-mh.php: Add search2 additional

If default search found nothing, use search2, it's slower but will
search in a larger range.
Also, search2 use 'Recieved:' date, this can fix 'Date:' mistake when
actual mail send date diff with it declared.