[PATCH 0 of 2] SSL: let it build against BorginSSL and LibreSSL (take #2)

[Piotr Sikora]

Hey Maxim,
just to speed this up, this is the version with #ifndefs added
only around SSL_CTX_set_tmp_rsa_callback().

Feel free to commit whichever version you prefer.

Best regards,
Piotr Sikora