Fixing Luarocks

Closes #32354.

Primarily, this fixes Luarocks. It also adds a shared, simple test to Lua & Lua51, tidies up all formulae involved, and revisions all 4 lua-something formulae. 

Theoretically, this could work without revisioning anything other than Luarocks, but doing it this way is much cleaner, smoother and reduces the risk of a lingering lua screwing this update up for users.
If I understand the way ``` luajit ``` depends on ``` lua51 ``` (*And I'm not claiming to particularly understand that relationship entirely*), I *think* the rock is built for ``` Lua51 ``` and then ``` Lua51 ``` kinda passes it over to ``` Luajit ```. Maybe.

I could be entirely wrong on that. I understand Lua, and Lua52, and even Luarocks, but I don't have an understanding of the ``` Lua51 ``` and ``` Luajit ``` marriage & the dynamics of that relationship.