0028636: Optimisation of gp_* classes in order to avoid unnecesary calling gp_Dir...

0028636: Optimisation of gp_* classes in order to avoid unnecesary calling gp_Dir* constructors with normalisation

The improvement is concluded in replacement of calls to gp_Dir2d(1,0) with calls to gp_Dir2d(void).
Thus we avoid sqrt() that is called from within gp_Dir2d(double,double). The same is with direction in 3D space.