override key-generation implementations by placing handlers in the methods
for DSA and DH. Also, parameter generation for DSA and DH is possible by
another new handler for each method.
write external engines (and thus should require only installed openssl
headers and libs to compile without warnings). So this gets rid of recently
introduced compilation warnings (no longer including internal headers) by
including string.h directly.
to be prefixed with e_ instead of hw_. They aren't necessarely hardware
engines. The files commited here are exact copies of the corresponding
hw_ files found in crypto/engine/.
