Currying RFC

Automatic currying of all functions and closures
if I return `|b| add(1, b)` from my function I will have to declare the function's return type to be `-> |int| -> int`

if they are `Vec<Rc<Cell<int>>>` then the return type of the function is `|Vec<Rc<Cell<int>>>| -> Vec<Rc<Cell<int>>>`