Support MD5 in the Botan plugin if supported by Botan.
MD5 is required for RADIUS and obviously EAP-MD5,
and also for non-PKCS#8 encoded, encrypted private keys.
Botan only allows RSA generating keys >= 1,024 bits, which makes
the RSA test suite fail. It is questionable whether it makes
sense to test 768 bit RSA keys anymore. They are too weak
from today's perspective anyway.