Fix up size and sign issues in base32 code

[tor/rransom.git] / changes / bug2331

  o Minor bugfixes:
    - Add assertions to check for overflow in arguments to
      base32_encode and base32_decode; fix a signed-unsigned
      comparison there too.  These bugs are actually reachable in Tor,
      but it's good to prevent future errors too.  Found by doorss.