[PATCH 2 of 2] SSL: let it build against BoringSSL

[Piotr Sikora]

Hey Maxim,

> I think that it's better idea to preserve the common code rather
> than to add unneded #ifndef's.

Well, my argument for #ifndefs is that both BoringSSL and LibreSSL
(for which I have patch in my queue) removed support for export cipher
suites, so I don't see a point in calling a function that we know
doesn't do anything and that might be removed sooner rather than
later.

BoringSSL made SSL_CTX_set_tmp_rsa_callback() a no-op (at least for
now) and just ignores the callback.

LibreSSL sets and calls the callback (because of the
SSL_OP_EPHEMERAL_RSA, which is still supported, even though it
violates TLS standard), but I expect it might get removed soon... and
then, depending on their implementation, it might put an error on the
error queue, which will just mess things for us.

I'm going to send the LibreSSL patch in a moment and let's see if the
#ifndefs are still bothering you, but I feel rather strongly about
keeping them.

> This one scares me though.  In particular, because BoringSSL
> managed to move various EVP_* functions to CIPHER library, and
> this looks strange.  I also wonder how many similar changes are
> unnoticed because they don't break build...

Rest seems to work fine :)

I'm rather committed to switching to BoringSSL myself in the near
future, so this is more than just "it compiles" change.

Best regards,
Piotr Sikora