Native line numbers landed on master

[Eli Zaretskii]

I've merged the line-numbers branch into master.  Please report any
problems you see as result of this via 'report-emacs-bug', as usual.

Thanks to everyone who tested the branch and provided feedback.

I will keep the branch in the repository for a week or so, before
deleting it, to let people who tracked the branch switch to master in
their own free time.