Order of hash function parameters in adaptor point

[raulcano]

I discovered a very minor inconsistency in specs regarding the hash function in the adaptor points (aka tweak points or signature points).

• In the introduction is described as S = R + H(R || P || m) * P (R before the P)
• In the numeric outcome section is described as si * G = Ri + H(P, Ri, di)*P (P before the Ri)
• In other sources (i.e. CryptoGarage), it's described as T = R + H(R || P || m)*P (R before the P)

Hence, for clarity and consistency, this pull request proposes to change the H(P, Ri, di) to H(Ri, P, di).

In all fairness, the notation H(P, Ri, di) does not imply that the byte chain will be built in the same order the parameters are present in the function call (the operator || implies concatenation, the comma , does not). However, for clarity, I believe we should make sure to use the same order and avoid potential confusion.

[Christewart]

ACK