gather_sites(ILattice<T,2>& d, const ILattice<T1,2>& s0, int i0, const ILattice<T1,2>& s1, int i1)
gather_sites(ILattice<T,4>& d, const ILattice<T1,4>& s0, int i0, const ILattice<T1,4>& s1, int i1, const ILattice<T1,4>& s2, int i2, const ILattice<T1,4>& s3, int i3)
gather_sites(ILattice<T,2>& d, 	     const ILattice<T1,2>& s0, int i0, 	     const ILattice<T1,2>& s1, int i1){  d.elem(0) = s0.elem(i0);  d.elem(1) = s0.elem(i1);}