e0ed8ed664 went too far and broke the
backward compat headers for Linux systems.

There are crypto hash function symbol overlaps between libmd and libcrypto on
FreeBSD, which causes hashing of the certificates store to fail as a
side-effect when using TLS constraints. Since all we really need is MD5, just
use the embedded OpenBSD versions instead.

Remove dependency on libcrypto, include hash headers in a nicer way.