Previously hierarchicalize (the ancestor of `makeSections`) would put header attributes on the containing Div. In 2.8 this behavior changed, which broke some tools depending on pandoc. Here we roll back this change, so that attributes again migrate from the header to the containing Div when `makeSections` is run. Note that attributes are retained on the header as well (unlike before) -- with the exception of the `id` attribute, which of course cannot be duplicated. Note that this is an empty commit. The previous commit, 8d0033111, was mistakenly recorded as an amendment to the --toc-depth fix, so the commit message for that is wrong; this message correctly describes the change in 8d0033111. Closes #5965.