This changes most URLs in llvm's html files to HTTPS. Most changes were search-and-replace with manual verification; some changes were manual. For a few URLs, the websites were performing redirects or had changed their anchors; I fixed those up manually. There are a very small number of dead links for which I don't know any replacements (they are equally dead as HTTP or HTTPS).
I have this structured as a series of git commits with mechanical and manual replacements separated, but I don't know how to present that through Differential (as GitHub PRs aren't available yet).
These will all now redirect. Maybe that's OK/better because they are now more uniform, though.