Comment out warnings

These warnings are very irritating. They do not
warn about deprecated or misused feature. They are
issued any time you compile the tests. They don't
provide any useful information unless you look at the
code and have insight in the implementation detains.

To sum up: They don't look like a warning addressed to
the user, but like a reminder on an intended future
implementation addressed to the implementor. Hence
they should not be exposed to the user.

If anyone feels that this is an important user warning
feel free to re-enable it after adding enough information
making the warning actually useful.

dune/istl/paamg/amg.hh

@@ -325,7 +325,7 @@ namespace Dune
         postSteps_(parms.getNoPostSmoothSteps()), buildHierarchy_(false),
         additive(parms.getAdditive()), coarsesolverconverged(true),
         coarseSmoother_(),
-#warning should category be retrieved from matrices?
+// #warning should category be retrieved from matrices?
         category_(SolverCategory::category(*smoothers_->coarsest())),
         verbosity_(parms.debugLevel())
     {

dune/istl/solver.hh

@@ -264,7 +264,7 @@ namespace Dune
         DUNE_THROW(InvalidSolverCategory, "LinearOperator and ScalarProduct must have the same SolverCategory!");
     }
 
-#warning actually we want to have this as the default and just implement the second one
+    // #warning actually we want to have this as the default and just implement the second one
     // //! \copydoc InverseOperator::apply(X&,Y&,InverseOperatorResult&)
     // virtual void apply (X& x, Y& b, InverseOperatorResult& res)
     // {