Firefox fixes.

Firefox fixes.

 + support for more than one initial packet
 + workaround for trailing zeroes in packet
 + ignore application data packet if no keys yet (issue in draft 27/ff nightly)
 + fixed PING frame parser
 + STREAM frames need to be acknowledged

The following HTTP configuration is used for firefox (v74):

http {

    ssl_certificate_key localhost.key;
    ssl_certificate localhost.crt;
    ssl_protocols TLSv1.2 TLSv1.3;

    server {
        listen 127.0.0.1:10368 reuseport http3;
        ssl_quic on;
        server_name  localhost;

        location / {
            return 200 "This-is-QUICK\n";
        }
    }
    server {
        listen 127.0.0.1:5555 ssl; # point the browser here
        server_name  localhost;
        location / {
            add_header Alt-Svc 'h3-24=":10368";ma=100';
            return 200 "ALT-SVC";
        }
    }
}