Makes KAMG and FastAMG solver available with dune-istl 2.3

Previously we relied on the define DUNE_HAS_FAST_AMG to detect
whether these preconditioners are available. This define is only
available in the 2.2 release with cmake support. Therfore we now
addtionally test whether we are using dune-isl 2.3 or newer.

cmake/Modules/opm-core-prereqs.cmake

@@ -3,6 +3,9 @@
 
 # defines that must be present in config.h for our headers
 set (opm-core_CONFIG_VAR
+  DUNE_ISTL_VERSION_MAJOR
+  DUNE_ISTL_VERSION_MINOR
+  DUNE_ISTL_VERSION_REVISION
 	HAVE_ERT
 	HAVE_SUITESPARSE_UMFPACK_H
 	)

opm/core/linalg/LinearSolverIstl.cpp

@@ -30,6 +30,7 @@
 
 // TODO: clean up includes.
 #include <dune/common/deprecated.hh>
+#include <dune/common/version.hh>
 #include <dune/istl/bvector.hh>
 #include <dune/istl/bcrsmatrix.hh>
 #include <dune/istl/operators.hh>
@@ -61,7 +62,7 @@ namespace Opm
         solveCG_AMG(const Mat& A, Vector& x, Vector& b, double tolerance, int maxit, int verbosity,
                     double prolongateFactor, int smoothsteps);
 
-#ifdef HAS_DUNE_FAST_AMG
+#if defined(HAS_DUNE_FAST_AMG) || DUNE_VERSION_NEWER(DUNE_ISTL, 2, 3)
         LinearSolverInterface::LinearSolverReport
         solveKAMG(const Mat& A, Vector& x, Vector& b, double tolerance, int maxit, int verbosity,
                   double prolongateFactor, int smoothsteps);