replace IsTrue by dune_static_assert

[[Imported from SVN: r885]]

istl/solvers.hh

@@ -643,8 +643,8 @@ namespace Dune {
                     double reduction, int maxit, int verbose) :
       ssp(), _op(op), _prec(prec), _sp(ssp), _reduction(reduction), _maxit(maxit), _verbose(verbose)
     {
-      IsTrue< static_cast<int>(L::category) == static_cast<int>(P::category) >::yes();
-      IsTrue< static_cast<int>(L::category) == static_cast<int>(SolverCategory::sequential) >::yes();
+      dune_static_assert(static_cast<int>(L::category) == static_cast<int>(P::category), "L and P must be of the same category!");
+      dune_static_assert(static_cast<int>(L::category) == static_cast<int>(SolverCategory::sequential), "L must be sequential!");
     }
     /*!
        \brief Set up solver.