samples: use evutil_socket_t instead and handle 64 bit Windows (#1682) * Use evutil_socket_t instead in http server sample and handle 64 bit Windows * Update http-server.c * consistently using EV_SOCK_FMT for Windows compatibility * code review: fix missing symbol strsignal * Add evutil_strsignal() helper instead of strsignal() macro --------- Co-authored-by: Hernan Martinez <hernan.c.martinez@gmail.com> Co-authored-by: Azat Khuzhin <azat@libevent.org>