libtls: make the TLS_EOF_NO_CLOSE_NOTIFY bit user-visible

[skarnet]

Context: I'm writing an asynchronous TLS tunnel engine supporting libtls as a backend, with an option to omit (or force) sending a close_notify and check if the peer sent one.

When the peer closes the connection, this is reported to the user as tls_read() returning 0, which is all good, but I need to know whether the peer sent a close_notify or not. Currently, this information is only available as ctx->state & TLS_EOF_NO_CLOSE_NOTIFY; it is used by tls_close(), but I have no way of retrieving it when I'm not the one initiating the close. And I cannot access ctx->state because struct tls is private.

It would be nice to have an accessor for this. It could be as simple as:

int tls_eof_no_close_notify(struct tls *ctx)
{
  return ctx->state & TLS_EOF_CLOSE_NOTIFY != 0;
}

Thanks in advance.