Lua >= Lua52

See [this](https://github.com/Homebrew/homebrew/pull/29236) PR for more details. The previous thread for this PR is [here](https://github.com/Homebrew/homebrew/pull/31996). I was planning to rebase but I made a fairly awful mistake mid-rebasing and things went horribly wrong, so here’s to starting fresh and hopefully not screwing everything up.

CC: @mikemcquaid @daurnimator @sdegutis @nijikon
Fixed in the latest commit. (Had other stuff to tidy up. Didn't dedicate an entire commit to removing the one line).