Build dynamic engines even if configured "no-shared"

Until now, the engines in engines/ were only built as dynamicaly
loadable ones if shared libraries were built.

We not dissociate the two and can build dynamicaly loadable engines
even if we only build static libcrypto and libssl.  This is controlled
with the option (enable|disable|no)-static-engine, defaulting to
no-static-engine.

Note that the engines in crypto/engine/ (dynamic and cryptodev) will
always be built into libcrypto.

Reviewed-by: Rich Salz <rsalz@openssl.org>