openssl: Add engine configuration to openssl.cnf

This adds engine configuration sections to openssl.cnf, with a commented
list of engines.  To enable an engine, all you have to do is uncomment
the engine line.

It also adds some useful comments to the devcrypto engine configuration
section.  Other engines currently don't have configuration commands.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>
(cherry picked from commit cebf024c4d9fd761e55383a582f7e29ac7cc921c)
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>