* The number of packets sent or lost in ECN validation must be tracked per
  QUIC packets and packet number space.
* Handle coalesced QUIC packets correctly.

Remove unused NGTCP2_ERR_UNKNOWN_PKT_TYPE

Fixes: https://github.com/ngtcp2/ngtcp2/issues/261

Fixes: https://github.com/ngtcp2/ngtcp2/issues/257

Fix handling of "*" as address in example server

Fix Windows build

Use winsock.h on windows instead of sys/socket.h

Without these changes, library was failing to build on both Windows and
FreeBSD.