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.
When we introduced NEED_KEY_1024 in routerparse.c back in
0.2.0.1-alpha, I forgot to add a *8 when logging the length of a
bad-length key.
Bugfix for 3318 on 0.2.0.1-alpha.