A few fixes/improvements:

A few fixes/improvements:
- first, BN_free == BN_clear_free in our libcrypto, so we do not need to
  treat CBIGNUM (crypto BN) separately from BIGNUM (regular BN).
- then, in bn_i2c(), since BN_bn2bin returns BN_num_bytes(input), take
  advantage of this to avoid calling BN_num_bytes() a second time.
  BN_num_bytes() is cheap, but this not a reason to perform redundant
  work.
- finally, in bn_c2i, if bn_new() fails, return early. Otherwise
  BN_bin2bn will try to create a BN too, and although this will probably
  fail since we were already out of memory, if we are on a threaded
  process and suddenly the allocation succeeds, we will leak it since it
  will never be stored in *pval.

ok jsing@