(rsa_sha256_sign, rsa_sha256_verify)

(rsa_sha256_sign_digest, rsa_sha256_verify_digest): New declarations.
(RSA_MINIMUM_N_OCTETS, RSA_MINIMUM_N_BITS): Increased to
62 octets and  489 bits, respectively, for supporting sha256.

Rev: src/nettle/rsa.h:1.27