Partially revert 1741ca28 (for Solver and SolverResult).

These classes might need some more revision before being approved
to be moved to the new namespace Dune::Solvers.

dune/solvers/solvers/solver.hh

@@ -5,9 +5,6 @@
 
 #include <dune/solvers/common/numproc.hh>
 
-namespace Dune {
-namespace Solvers {
-
 /**  \brief struct to store result related information such as for example number of iterations etc.
   *
   *  \warning The interface and implementation is so far highly experimental and will change without further notice!
@@ -71,11 +68,5 @@ class Solver : public NumProc
         SolverResult result;
 };
 
-} /* namespace Solvers */
-} /* namespace Dune */
-
-// For backward compatibility: will be removed eventually
-using Dune::Solvers::Solver;
-using Dune::Solvers::SolverResult;
 
 #endif