Reject 128-byte keys that are not 1024-bit
When we added the check for key size, we required that the keys be 128 bytes. But RSA_size (which defers to BN_num_bytes) will return 128 for keys of length 1017..1024. This patch adds a new crypto_pk_num_bits() that returns the actual number of significant bits in the modulus, and uses that to enforce key sizes. Also, credit the original bug3318 in the changes file.