Remove sign/verify and required_pkey_type fields of EVP_MD: these are a
legacy from when digests were linked to public key types. All signing is
now handled by the corresponding EVP_PKEY_METHOD.
Only allow supported digest types in RSA EVP_PKEY_METHOD: other algorithms
already block unsupported types.
Remove now obsolete EVP_dss1() and EVP_ecdsa().
Reviewed-by: Richard Levitte <levitte@openssl.org>
7f572e958b