More test cases.
More test cases.

Add DSA tests.

Add tests to verify signatures against public keys. This will also check
that a public key is read in correctly.

Reviewed-by: Ben Laurie <73675debcd8a436be48ec22211dcf44fe0df0a64@openssl.org>

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl