Fixes one comment that mentioned the wrong function name. Also causes
two BN random functions to fail when the output is NULL. Previously they
would silently do nothing.

Change-Id: I89796ab855ea32787765c301a478352287e61190

Previously we generated a number that was 8 bytes too large and used a
modular reduction, which has a (tiny, tiny) bias towards zero.

Out of an excess of caution, instead truncate the generated nonce and
try again if it's out of range.

Change-Id: Ia9a7a57dd6d3e5f13d0b881b3e9b2e986d46e4ca

This change causes (EC)DSA nonces be to calculated by hashing the
message and private key along with entropy.

Initial fork from f2d678e6e8 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)