SETTINGS ID is little endian in wire format despite the fact that spec/2 says it is network byte order.

Include sys/types.h for ssize_t

Now -nvh option works.

This is because our priority queue implementation does not have stable sort
property, so queueing SYN_STREAM, DATA in this order does not necessarily
mean SYN_STREAM will be sent first.

Discard inbound HEADERS and DATA in CLOSING state. Handle stream shutdown when DATA is received with FIN bit set.