Disable SSLv3 by default.

SSLv3 has been long known to have weaknesses and the POODLE attack has
once again shown that it is effectively broken/insecure. As such, it is
time to stop enabling a protocol was deprecated almost 15 years ago.

If an application really wants to provide backwards compatibility, at the
cost of security, for now SSL_CTX_clear_option(ctx, SSL_OP_NO_SSLv3) can be
used to re-enable it on a per-application basis.

General agreement from many.

ok miod@
basic formatting fixes;
Fuck it. No SSLv3; not now, not ever. The API of the future will only
support the protocols of the future.

(Perhaps a bit late in burning this bridge entirely, but there's no time
like the present, esp. with other players now leaning against back compat.)