** to ask for new chat content.  The "name" argument should begin with
** an integer which is the largest "msgid" that the chat page currently
** holds.  If newer content is available, this routine returns that
** content straight away.  If no new content is available, this webpage
** blocks until the new content becomes available.  In this way, the
** system implements "hanging-GET" or "long-poll" style event notification.
**
**      /chat-poll/N
**
** If N is negative, then the return value is the N most recent messages.
** Hence a request like /chat-poll/-100 can be used to initialize a new
** chat session to just the most recent messages.
**
** The reply from this webpage is JSON that describes the new content.
** Format of the json:
**
** |    {
** |      "msg":[
** |        {
** |           "msgid": integer // message id

  int msgid = atoi(PD("name","0"));
  Stmt q1;
  login_check_credentials();
  if( !g.perm.Chat ) return;
  chat_create_tables();
  cgi_set_content_type("text/json");
  dataVersion = db_int64(0, "PRAGMA data_version");
  if( msgid<0 ){
    msgid = db_int(0,
        "SELECT msgid FROM chat WHERE mdel IS NOT true"
        " ORDER BY msgid DESC LIMIT 1 OFFSET %d", -msgid);
  }
  db_prepare(&q1,
    "SELECT msgid, datetime(mtime), xfrom, xmsg, length(file),"
    "       fname, fmime, mdel"
    "  FROM chat"
    " WHERE msgid>%d"
    " ORDER BY msgid",
    msgid