Add Factorio Lua

[JohnTheCoolingFan]

Factorio Lua is a custom modified lua 5.2.1, used in the game Factorio.
This PR adds the ability to use Factorio lua which is available on github: https://github.com/Rseding91/Factorio-Lua
Some of the extra functionality has been added into the library. All the extra functions or changed functions are linked.
This PR also requires some modifications to lua-src-rs, for which I will also open a PR.

[JohnTheCoolingFan]

This is not an april fools joke. Just making clear in case there was some confusion.

[khvzak]

I'm really sorry but I don't think it's reasonable to dissipate resources to support custom Lua forks made by game developers, considering that there are no innovations in that forks (Luau is a good example of such innovations).

Also that forks simply can have severe bugs. I assume source code has not been properly auditeted and no strong community around them.
mlua already supports way too much in my opinion, more than even popular sol.

Also mlua is flexible enough and allows to link to any custom Lua fork that keeps backward compatibility (non-vendored mode).

[JohnTheCoolingFan]

I think I can maintain factorio lua in mlua, if you don't want to spend your own time on it.
This fork adds a set of new c++-level methods that can be takes advantage of in mlua, such as lua_tablesize. Also it has disabled IO and Coroutine modules in source code, so it's not backwards-compatible afaik. And providing vendored factorio lua version is better from the point of end user than requiring them to comoile lua themselves and linking it manually.
I would like factorio lua to be merged into mlua to avoid a situation of many forks of basically the same thing but with minor changes. If this PR doesn't get merged, I'll try to publish my forks on crates.io then.

[JohnTheCoolingFan]

Wube (developers of factorio) are known for how low the amount of bugs in their game is, so the same might be translated to their lua fork. Afaik there weren't any issues caused by factorio's lua fork. The community around it is quite big, mostly mod makers.
What I like on mlua is how easy it is to work with high-level stuff.

Making a separate fork which is the same with just addition of another lua in my opinion isn't good, especially while the main repo is still actively developed.

If you don't want to maintain factorio lua parts, then I volunteer as a maintainer for that part.

[JohnTheCoolingFan]

Closing this PR because it looks like it will not get merged