Merge pull request #15609 from bangerth/typename

Standardize on 'template <typename X>.

diff --cc include/deal.II/base/mutable_bind.h
Simple merge

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

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

diff --cc include/deal.II/non_matching/fe_values.h
Simple merge

diff --cc source/base/data_out_base.cc
Simple merge

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

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