Neuter the SSL_set_debug(3) API

Neuter the SSL_set_debug(3) API

The TLSv1.3 stack didn't support this in the first place, and in the legacy
stack it only added some dubious BIO_flush(3) calls. The sleep call between
SSL_read(3) and SSL_write(3) advertised in the comment next to the flag has
been a sleep call in the s_server since time immemorial, nota bene between
calls to BIO_gets(3). Anyway. This can all go and what remains will go with
the next major bump.

ok jsing