CG test written and passes i.e. converges with small true residual

in RedBlack MpcDagMpc, Unprec MdagM and Schur red black solver for
each of.

DomainWallFermion
MobiusFermion
MobiusZolotarevFermion
ScaledShamirFermion
ScaledShamirZolotarevFermion

tests/Test_dwf_cg_schur.cc

@@ -0,0 +1,53 @@
+#include <Grid.h>
+
+using namespace std;
+using namespace Grid;
+using namespace Grid::QCD;
+
+template<class d>
+struct scal {
+  d internal;
+};
+
+  Gamma::GammaMatrix Gmu [] = {
+    Gamma::GammaX,
+    Gamma::GammaY,
+    Gamma::GammaZ,
+    Gamma::GammaT
+  };
+
+int main (int argc, char ** argv)
+{
+  Grid_init(&argc,&argv);
+
+  const int Ls=8;
+
+  GridCartesian         * UGrid   = SpaceTimeGrid::makeFourDimGrid(GridDefaultLatt(), GridDefaultSimd(Nd,vComplexF::Nsimd()),GridDefaultMpi());
+  GridRedBlackCartesian * UrbGrid = SpaceTimeGrid::makeFourDimRedBlackGrid(UGrid);
+  GridCartesian         * FGrid   = SpaceTimeGrid::makeFiveDimGrid(Ls,UGrid);
+  GridRedBlackCartesian * FrbGrid = SpaceTimeGrid::makeFiveDimRedBlackGrid(Ls,UGrid);
+
+  std::vector<int> seeds4({1,2,3,4});
+  std::vector<int> seeds5({5,6,7,8});
+  GridParallelRNG          RNG5(FGrid);  RNG5.SeedFixedIntegers(seeds5);
+  GridParallelRNG          RNG4(UGrid);  RNG4.SeedFixedIntegers(seeds4);
+
+  LatticeFermion    src(FGrid); random(RNG5,src);
+  LatticeFermion result(FGrid); result=zero;
+  LatticeGaugeField Umu(UGrid); random(RNG4,Umu);
+
+  std::vector<LatticeColourMatrix> U(4,UGrid);
+  for(int mu=0;mu<Nd;mu++){
+    U[mu] = peekIndex<LorentzIndex>(Umu,mu);
+  }
+  
+  RealD mass=0.1;
+  RealD M5=1.8;
+  DomainWallFermion Ddwf(Umu,*FGrid,*FrbGrid,*UGrid,*UrbGrid,mass,M5);
+
+  ConjugateGradient<LatticeFermion> CG(1.0e-8,10000);
+  SchurRedBlackSolve<LatticeFermion> SchurSolver(CG);
+  SchurSolver(Ddwf,src,result);
+
+  Grid_finalize();
+}