[Audit] Unnecessary re-computation of stored value

[AnomalRoil]

In the signing round 1, the value round.temp.point is stored, but in round 4 and in round 5, the bigGamma value and the RX, RY values respectively are re-computed from the round.temp.gamma value, instead of being retrieved from the round.temp.point variable from round 1.

Since this implies modular exponentiations, performances could be improved by using the stored value.