CACreateCert: choose a stronger default hash for longer keys
CACreateCert: choose a stronger default hash for longer keys

If the public key or signing key has a security strength of more
than 128 bits then sha-256 is not appropriate as a default hash
as it has only 128 bits of security strength.  Choose a stronger
hash as the default hash in this case and warn if it's not
available.

mackyle/ezcert,mackyle/ezcert