Merge from mainline.

git-svn-id: https://svn.dealii.org/branches/branch_petscscalar_complex@32728 0785d39b-7218-0410-832d-ea1e28bc413d

diff --cc deal.II/include/deal.II/lac/constraint_matrix.templates.h
Simple merge

diff --cc deal.II/source/numerics/derivative_approximation.inst.in
Simple merge

diff --cc deal.II/source/numerics/matrix_tools.cc
index 0c98dc8b09f2988f84276b9aff5070e207befe34,6a726729c127a62bb53e14b7e8c6616667c20e93..b2bd2e437134bb7e64ff72f80a24e0e1bf213c8a
--- 1/deal.II/source/numerics/matrix_tools.cc
--- 2/deal.II/source/numerics/matrix_tools.cc
+++ b/deal.II/source/numerics/matrix_tools.cc
@@@ -2350,19 -2350,19 +2350,20 @@@ namespace MatrixTool
          // entry from within the part of the
          // matrix that we can see. if we can't
          // find such an entry, take one
 -        PetscScalar average_nonzero_diagonal_entry = 1;
 -        for (types::global_dof_index i=local_range.first; i<local_range.second; ++i)
 -          if (matrix.diag_element(i) != 0)
 -            {
 -              average_nonzero_diagonal_entry = std::fabs(matrix.diag_element(i));
 -              break;
 -            }
 +      PetscScalar average_nonzero_diagonal_entry = 1;
 +      for (types::global_dof_index i=local_range.first; i<local_range.second; ++i)
 +        if (matrix.diag_element(i) != PetscScalar ())
 +          {
 +            average_nonzero_diagonal_entry = matrix.diag_element(i);
 +            break;
 +          }
 +
+ 
          // figure out which rows of the matrix we
          // have to eliminate on this processor
          std::vector<types::global_dof_index> constrained_rows;
          for (std::map<types::global_dof_index,double>::const_iterator
--             dof  = boundary_values.begin();
++           dof  = boundary_values.begin();
               dof != boundary_values.end();
               ++dof)
            if ((dof->first >= local_range.first) &&