SuperLU backend now checks the solution vector for nan's/inf's which can

appear if the solver has not found a solution

   - if there are nan's or inf's in the solution vector, converged (the return of the solve() function) is set
     to false
   - reviewed by Klaus



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@8251 2fb0f335-1f38-0410-981e-8018bf24f1b0