Cherry-pick doc updates from PR 1554

Also fix version in libcrypto.num, from backporting new
functions.

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1554)
(cherry picked from commit ebcb5368)