HTTP/3: "quic" parameter of "listen" directive. Now "listen" directve has a new "quic" parameter which enables QUIC protocol for the address. Further, to enable HTTP/3, a new directive "http3" is introduced. The hq-interop protocol is enabled by "http3_hq" as before. Now application protocol is chosen by ALPN. Previously used "http3" parameter of "listen" is deprecated.