Merge pull request #10448 from bangerth/tria_object

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

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

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

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

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

diff --cc source/grid/tria.cc
Simple merge