message: Enable IPv4 mapping rather then exluding OpenBSD
  Listing each OS that hasn't AI_V4MAPPED defined is both verbose and
  brittle. Simply checking whether AI_V4MAPPED exists before attempting to
  use it always works, regardless of the OS.
diff: @@ -288,7 +288,7 @@ bool interfaces::get_endpoint(const std::string& host, uint16_t port,
  hint.ai_socktype = SOCK_DGRAM;
  if (preferred)
  hint.ai_family = *preferred == protocol::network::ipv4 ? AF_INET : AF_INET6;
  -#ifndef __OpenBSD__
  +#ifdef AI_V4MAPPED
  if (hint.ai_family == AF_INET6)
  hint.ai_flags = AI_V4MAPPED;
  #endif
  