Allow functions to receive mutable references to variables outside of that function's scope

[jmeaster30]

The reference concept is meant to resemble heap allocated memory so inside a function the user should be able to load and modify the values of those references.

But you can build a reference inside a function to access variables outside the function. This is only allowed if the reference is passed as a function argument.

[jmeaster30]

holding off until I find a use case for it

[jmeaster30]

87 may make this obsolete