MSG_KILLREAD, MSG_READ, MSG_REPLIED, SUB_ANON, SUB_AONLY, SUB_NAME, SUB_PRIV,
SUB_PONLY, MSG_PRIVATE, MSG_ANONYMOUS, MSG_MODERATED, MSG_VALIDATED
Fix up get_*_msgs() in msgslib.ssjs and add idx_to_user() function (Checks
if the passed message index is to the current user)