FFI support for lune

[qwreey]

There is still a lot of work to be done, Most of the specs are well polished.
I have discussed it with many people (mostly, Korean) to ensure that it is done cleanly while supporting as many cases as possible, but it has not been released to the lune community yet.

At first time, It was a personal fork that I did not intend to merge into lune, but the specs and implementation have improved a lot, so I think the quality will be sufficient, so I am discussing it publicly and developing it publicly.

Since the specifications-related parts are still in Korean, we would like to translate them into English as soon as possible.
There are many comments written in the code that will be helpful. (Comments are written in English.)

The direction this library pursues is to allow Lua to select which data areas Lua can handle and which areas will be automatically managed.
Lua can create a space on the heap that it can manage as needed, provide that space to the outside as a pointer, or use it to hold data that Lua cannot handle. (such as unsigned 64 bit int, c struct)

Except for pointer operations, all operations are safe. I'm looking for a safer way to handle pointer arithmetic. If you have any comments about this, please write them here.

I will update progress as soon as specifications translating is done in this thread.

[CompeyDev]

@qwreey Small thing - is it possible to link this to the relevant issue?