Merge from Mainline

git-svn-id: https://svn.dealii.org/branches/branch_cmake@28566 0785d39b-7218-0410-832d-ea1e28bc413d

diff --cc deal.II/examples/step-18/step-18.cc
Simple merge

diff --cc deal.II/examples/step-32/step-32.cc
Simple merge

diff --cc deal.II/examples/step-42/step-42.cc
Simple merge

diff --cc deal.II/include/deal.II/grid/grid_tools.h
Simple merge

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

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

diff --cc deal.II/source/grid/grid_tools.cc
Simple merge