- Compiles with g++-4,4 now. Error was error: declaration of
  ‘Dune::SuperLUMatrix<Dune::BCRSMatrix<Dune::FieldMatrix<K, n, p>,
  TA> >& m’shadows template parm ‘int m’ 
  Fixes flyspray #581

- Removed wrong assertion. One should not check whether the whole
  matrix is copied if one just copies a part of it. (Blame copy & paste)

[[Imported from SVN: r1053]]