Global variable can't be wrapped by reference

[deadlocklogic]

Consider:

static int x = 1;

And binding with:

state["num"] = sol::var(std::ref(x));

Now print(num) gives function:000000... (hex address), which should be a number instead. I even tried with global usertypes and got same issue. (When accessing the variable I get cannot index function etc...)

If we can fix #1416 , would be great too! (As I remember many other issues were related to it). So far the most serious issues in sol are static and global variable.

@ThePhD By the way I am working on a binding auto-generator which implements a lua/sol generator, when ready I will post an issue here if anyone ever gets interested.

Thanks for your efforts again!