kit: use CSS counters to render line numbers where possible Affects changeset, file view, file diff and file annotate pages. Doesn't affect file comparison page (aka side-by-side file diff). Page size, regular file view (mercurial/commands.py): - 987963 B before - 596244 B after Page size, changeset (4441705b7111): - 1319976 B before - 923672 B after