Revert "H2O: Don't set several socket options (#5007)" (#5032)

This reverts commit 04740508137d72fa07ea6e7d99ab5e3a7fa5ad5c.
It turns out that the socket options in question don't have
any significant performance impact in the benchmark environment,
but they are beneficial in theory, so it is preferable to set them.

frameworks/C/h2o/src/event_loop.c

@@ -137,6 +137,11 @@ static int get_listener_socket(const char *bind_address, uint16_t port)
 
 		LOCAL_CHECK_ERRNO(setsockopt, s, SOL_SOCKET, SO_REUSEADDR, &option, sizeof(option));
 		LOCAL_CHECK_ERRNO(setsockopt, s, SOL_SOCKET, SO_REUSEPORT, &option, sizeof(option));
+		LOCAL_CHECK_ERRNO(setsockopt, s, IPPROTO_TCP, TCP_QUICKACK, &option, sizeof(option));
+		option = H2O_DEFAULT_HANDSHAKE_TIMEOUT_IN_SECS;
+		LOCAL_CHECK_ERRNO(setsockopt, s, IPPROTO_TCP, TCP_DEFER_ACCEPT, &option, sizeof(option));
+		option = DEFAULT_TCP_FASTOPEN_QUEUE_LEN;
+		LOCAL_CHECK_ERRNO(setsockopt, s, IPPROTO_TCP, TCP_FASTOPEN, &option, sizeof(option));
 		LOCAL_CHECK_ERRNO(bind, s, iter->ai_addr, iter->ai_addrlen);
 		LOCAL_CHECK_ERRNO(listen, s, INT_MAX);
 		ret = s;