Signature details omit information about ECDSA nonces

[znewman01]

The Appendix F ("Signing Transactions") spells out the use of recoverable ECDSA signatures, but doesn't mention how nonces are computed or included.

In particular, this creates a couple of minor problems:

• ECDSASIGN is not a function unless the nonce is supplied, so the text is incorrect
• the supplied reference [Johnson 2001] suggests that nonces be computed randomly, but the Go Ethereum client uses RFC 6979 deterministic signatures. One might argue that this is a choice left to the client, or one might consider it part of the specification (in particular, using deterministic nonces removes the possibility of a class of errors); either way, I think readers would benefit from a sentence of discussion