openssl: Add engine configuration to openssl.cnf

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>