openssl: configure engine packages during install

openssl: configure engine packages during install

This enables an engine during its package's installation, by adding it
to the engines list in /etc/ssl/engines.cnf.d/engines.cnf.

The engine build system was reworked, with the addition of an engine.mk
file that groups some of the engine packages' definitions, and could be
used by out of tree engines as well.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>