message: Correct error for unknown protocol type in socket
diff: @@ -241,7 +241,7 @@ impl PalSocket for Sys {
  SOCK_STREAM => e(syscall::open("tcp:", flags)) as c_int,
  SOCK_DGRAM => e(syscall::open("udp:", flags)) as c_int,
  _ => {
  - errno = syscall::EPROTOTYPE;
  + errno = syscall::EPROTONOSUPPORT;
  -1
  }
  }
  