[examples] Use more fine-grained version testing for FastAMG

* The way the `FastAMG` preconditioner is set up only works in 2.10.
* Using non-blocked matrices only works in master (>2.10) which is
  now tested as >=2.11, because in the 2.10 CI job, checking fo >2.10
  succeeds.

examples/poisson-pq2.cc

@@ -202,7 +202,8 @@ int main (int argc, char *argv[]) try
   // Technicality:  turn the matrix into a linear operator
   MatrixAdapter<Matrix,Vector,Vector> op(stiffnessMatrix);
 
-#if DUNE_VERSION_GT(DUNE_ISTL, 2, 10)
+// FastAMG is not working for non-blocked matrices in 2.10
+#if DUNE_VERSION_GTE(DUNE_ISTL, 2, 11)
   auto preconditioner = makeAMGPreconditioner<Vector>(stiffnessMatrix);
 #else
   // Sequential incomplete LU decomposition as the preconditioner

examples/stokes-taylorhood.cc

@@ -22,12 +22,6 @@
 #include <dune/istl/multitypeblockmatrix.hh>
 #include <dune/istl/multitypeblockvector.hh>
 
-
-#if DUNE_VERSION_GT(DUNE_ISTL, 2, 10)
-#include <dune/istl/paamg/fastamg.hh>
-#endif
-
-
 #include <dune/functions/functionspacebases/interpolate.hh>
 #include <dune/functions/functionspacebases/taylorhoodbasis.hh>
 #include <dune/functions/backends/istlvectorbackend.hh>
@@ -66,7 +60,7 @@ using namespace Dune;
 
 
 
-#if DUNE_VERSION_GT(DUNE_ISTL, 2, 10)
+#if DUNE_VERSION_GTE(DUNE_ISTL, 2, 10)
 
 template<class V, class... P>
 class BlockDiagonalPreconditioner : public Preconditioner<V,V> {
@@ -310,7 +304,7 @@ int main (int argc, char *argv[]) try
   // Technicality:  turn the matrix into a linear operator
   MatrixAdapter<Matrix,Vector,Vector> stiffnessOperator(stiffnessMatrix);
 
-#if DUNE_VERSION_GT(DUNE_ISTL, 2, 10)
+#if DUNE_VERSION_GTE(DUNE_ISTL, 2, 10)
   // As iterative solver we use MinRes with a block-diagonal preconditioner
   // for the saddle point problem. An optimal preconditioner would be obtained,
   // if the (0,0)-velocity-block is exact, while the (1,1)-block is the Schur-

examples/utilities.hh

@@ -10,7 +10,7 @@
 #include <dune/common/typetraits.hh>
 #include <dune/common/concept.hh>
 
-#if DUNE_VERSION_GT(DUNE_ISTL, 2, 10)
+#if DUNE_VERSION_GTE(DUNE_ISTL, 2, 10)
 #include <dune/istl/paamg/fastamg.hh>
 #endif