Upgraded Q -> 2 from #279 [1683710498041]

Judge has assessed an item in Issue 279 as 2 risk. The relevant finding follows: L-06 EllipticCurve.validateSignature has wrong and needless code blocks if P2 == 0 return false; uint256 Px = inverseModP2, p; Px = mulmodP0, mulmodPx, Px, p, p; Px = p0 inverseP2^2 is not correct here. Fortunately, ...