public static Ed25519GroupElement doubleGroupElement(final Ed25519GroupElement g){
  return addGroupElements(g,g);
}

public static Ed25519GroupElement doubleGroupElement ( final Ed25519GroupElement g ) { return addGroupElements ( g , g ) ; }
doubles a group element and returns the result in the p3 coordinate system . it uses biginteger arithmetic and the affine coordinate system . this method is a helper used to test the projective group doubling formula in ed25519groupelement .
